strutil.c

Go to the documentation of this file.

/*
 * This file is part of the libsigrok project.
 *
 * Copyright (C) 2010 Uwe Hermann <uwe@hermann-uwe.de>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

/* Needed for POSIX.1-2008 locale functions */
/** @cond PRIVATE */
#define _XOPEN_SOURCE 700
/** @endcond */
#include <config.h>
#include <ctype.h>
#include <locale.h>
#if defined(__FreeBSD__) || defined(__APPLE__)
#include <xlocale.h>
#endif
#if defined(__FreeBSD__)
#include <sys/param.h>
#endif
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <errno.h>
#include <libsigrok/libsigrok.h>
#include "libsigrok-internal.h"

/** @cond PRIVATE */
#define LOG_PREFIX "strutil"
/** @endcond */

/**
 * @file
 *
 * Helper functions for handling or converting libsigrok-related strings.
 */

/**
 * @defgroup grp_strutil String utilities
 *
 * Helper functions for handling or converting libsigrok-related strings.
 *
 * @{
 */

/**
 * Convert a string representation of a numeric value (base 10) to a long integer. The
 * conversion is strict and will fail if the complete string does not represent
 * a valid long integer. The function sets errno according to the details of the
 * failure.
 *
 * @param str The string representation to convert.
 * @param ret Pointer to long where the result of the conversion will be stored.
 *
 * @retval SR_OK Conversion successful.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int sr_atol(const char *str, long *ret)
{
        long tmp;
        char *endptr = NULL;

        errno = 0;
        tmp = strtol(str, &endptr, 10);

        while (endptr && isspace(*endptr))
                endptr++;

        if (!endptr || *endptr || errno) {
                if (!errno)
                        errno = EINVAL;
                return SR_ERR;
        }

        *ret = tmp;
        return SR_OK;
}

/**
 * Convert a text to a number including support for non-decimal bases.
 * Also optionally returns the position after the number, where callers
 * can either error out, or support application specific suffixes.
 *
 * @param[in] str The input text to convert.
 * @param[out] ret The conversion result.
 * @param[out] end The position after the number.
 * @param[in] base The number format's base, can be 0.
 *
 * @retval SR_OK Conversion successful.
 * @retval SR_ERR Conversion failed.
 *
 * @private
 *
 * This routine is more general than @ref sr_atol(), which strictly
 * expects the input text to contain just a decimal number, and nothing
 * else in addition. The @ref sr_atol_base() routine accepts trailing
 * text after the number, and supports non-decimal numbers (bin, hex),
 * including automatic detection from prefix text.
 */
SR_PRIV int sr_atol_base(const char *str, long *ret, char **end, int base)
{
        long num;
        char *endptr;

        /* Add "0b" prefix support which strtol(3) may be missing. */
        while (str && isspace(*str))
                str++;
        if (!base && strncmp(str, "0b", strlen("0b")) == 0) {
                str += strlen("0b");
                base = 2;
        }

        /* Run the number conversion. Quick bail out if that fails. */
        errno = 0;
        endptr = NULL;
        num = strtol(str, &endptr, base);
        if (!endptr || errno) {
                if (!errno)
                        errno = EINVAL;
                return SR_ERR;
        }
        *ret = num;

        /* Advance to optional non-space trailing suffix. */
        while (endptr && isspace(*endptr))
                endptr++;
        if (end)
                *end = endptr;

        return SR_OK;
}

/**
 * Convert a text to a number including support for non-decimal bases.
 * Also optionally returns the position after the number, where callers
 * can either error out, or support application specific suffixes.
 *
 * @param[in] str The input text to convert.
 * @param[out] ret The conversion result.
 * @param[out] end The position after the number.
 * @param[in] base The number format's base, can be 0.
 *
 * @retval SR_OK Conversion successful.
 * @retval SR_ERR Conversion failed.
 *
 * @private
 *
 * This routine is more general than @ref sr_atol(), which strictly
 * expects the input text to contain just a decimal number, and nothing
 * else in addition. The @ref sr_atoul_base() routine accepts trailing
 * text after the number, and supports non-decimal numbers (bin, hex),
 * including automatic detection from prefix text.
 */
SR_PRIV int sr_atoul_base(const char *str, unsigned long *ret, char **end, int base)
{
        unsigned long num;
        char *endptr;

        /* Add "0b" prefix support which strtol(3) may be missing. */
        while (str && isspace(*str))
                str++;
        if ((!base || base == 2) && strncmp(str, "0b", strlen("0b")) == 0) {
                str += strlen("0b");
                base = 2;
        }

        /* Run the number conversion. Quick bail out if that fails. */
        errno = 0;
        endptr = NULL;
        num = strtoul(str, &endptr, base);
        if (!endptr || errno) {
                if (!errno)
                        errno = EINVAL;
                return SR_ERR;
        }
        *ret = num;

        /* Advance to optional non-space trailing suffix. */
        while (endptr && isspace(*endptr))
                endptr++;
        if (end)
                *end = endptr;

        return SR_OK;
}

/**
 * Convert a string representation of a numeric value (base 10) to an integer. The
 * conversion is strict and will fail if the complete string does not represent
 * a valid integer. The function sets errno according to the details of the
 * failure.
 *
 * @param str The string representation to convert.
 * @param ret Pointer to int where the result of the conversion will be stored.
 *
 * @retval SR_OK Conversion successful.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int sr_atoi(const char *str, int *ret)
{
        long tmp;

        if (sr_atol(str, &tmp) != SR_OK)
                return SR_ERR;

        if ((int) tmp != tmp) {
                errno = ERANGE;
                return SR_ERR;
        }

        *ret = (int) tmp;
        return SR_OK;
}

/**
 * Convert a string representation of a numeric value to a double. The
 * conversion is strict and will fail if the complete string does not represent
 * a valid double. The function sets errno according to the details of the
 * failure.
 *
 * @param str The string representation to convert.
 * @param ret Pointer to double where the result of the conversion will be stored.
 *
 * @retval SR_OK Conversion successful.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int sr_atod(const char *str, double *ret)
{
        double tmp;
        char *endptr = NULL;

        errno = 0;
        tmp = strtof(str, &endptr);

        while (endptr && isspace(*endptr))
                endptr++;

        if (!endptr || *endptr || errno) {
                if (!errno)
                        errno = EINVAL;
                return SR_ERR;
        }

        *ret = tmp;
        return SR_OK;
}

/**
 * Convert a string representation of a numeric value to a float. The
 * conversion is strict and will fail if the complete string does not represent
 * a valid float. The function sets errno according to the details of the
 * failure.
 *
 * @param str The string representation to convert.
 * @param ret Pointer to float where the result of the conversion will be stored.
 *
 * @retval SR_OK Conversion successful.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int sr_atof(const char *str, float *ret)
{
        double tmp;

        if (sr_atod(str, &tmp) != SR_OK)
                return SR_ERR;

        if ((float) tmp != tmp) {
                errno = ERANGE;
                return SR_ERR;
        }

        *ret = (float) tmp;
        return SR_OK;
}

/**
 * Convert a string representation of a numeric value to a double. The
 * conversion is strict and will fail if the complete string does not represent
 * a valid double. The function sets errno according to the details of the
 * failure. This version ignores the locale.
 *
 * @param str The string representation to convert.
 * @param ret Pointer to double where the result of the conversion will be stored.
 *
 * @retval SR_OK Conversion successful.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int sr_atod_ascii(const char *str, double *ret)
{
        double tmp;
        char *endptr = NULL;

        errno = 0;
        tmp = g_ascii_strtod(str, &endptr);

        if (!endptr || *endptr || errno) {
                if (!errno)
                        errno = EINVAL;
                return SR_ERR;
        }

        *ret = tmp;
        return SR_OK;
}

/**
 * Convert text to a floating point value, and get its precision.
 *
 * @param[in] str The input text to convert.
 * @param[out] ret The conversion result, a double precision float number.
 * @param[out] digits The number of significant decimals.
 *
 * @returns SR_OK in case of successful text to number conversion.
 * @returns SR_ERR when conversion fails.
 *
 * @since 0.6.0
 */
SR_PRIV int sr_atod_ascii_digits(const char *str, double *ret, int *digits)
{
        const char *p;
        int *dig_ref, m_dig, exp;
        char c;
        double f;

        /*
         * Convert floating point text to the number value, _and_ get
         * the value's precision in the process. Steps taken to do it:
         * - Skip leading whitespace.
         * - Count the number of decimals after the mantissa's period.
         * - Get the exponent's signed value.
         *
         * This implementation still uses common code for the actual
         * conversion, but "violates API layers" by duplicating the
         * text scan, to get the number of significant digits.
         */
        p = str;
        while (*p && isspace(*p))
                p++;
        if (*p == '-' || *p == '+')
                p++;
        m_dig = 0;
        exp = 0;
        dig_ref = NULL;
        while (*p) {
                c = *p++;
                if (toupper(c) == 'E') {
                        exp = strtol(p, NULL, 10);
                        break;
                }
                if (c == '.') {
                        m_dig = 0;
                        dig_ref = &m_dig;
                        continue;
                }
                if (isdigit(c)) {
                        if (dig_ref)
                                (*dig_ref)++;
                        continue;
                }
                /* Need not warn, conversion will fail. */
                break;
        }
        sr_spew("atod digits: txt \"%s\" -> m %d, e %d -> digits %d",
                str, m_dig, exp, m_dig + -exp);
        m_dig += -exp;

        if (sr_atod_ascii(str, &f) != SR_OK)
                return SR_ERR;
        if (ret)
                *ret = f;
        if (digits)
                *digits = m_dig;

        return SR_OK;
}

/**
 * Convert a string representation of a numeric value to a float. The
 * conversion is strict and will fail if the complete string does not represent
 * a valid float. The function sets errno according to the details of the
 * failure. This version ignores the locale.
 *
 * @param str The string representation to convert.
 * @param ret Pointer to float where the result of the conversion will be stored.
 *
 * @retval SR_OK Conversion successful.
 * @retval SR_ERR Failure.
 *
 * @private
 */
SR_PRIV int sr_atof_ascii(const char *str, float *ret)
{
        double tmp;
        char *endptr = NULL;

        errno = 0;
        tmp = g_ascii_strtod(str, &endptr);

        if (!endptr || *endptr || errno) {
                if (!errno)
                        errno = EINVAL;
                return SR_ERR;
        }

        /* FIXME This fails unexpectedly. Some other method to safel downcast
         * needs to be found. Checking against FLT_MAX doesn't work as well. */
        /*
        if ((float) tmp != tmp) {
                errno = ERANGE;
                sr_dbg("ERANGEEEE %e != %e", (float) tmp, tmp);
                return SR_ERR;
        }
        */

        *ret = (float) tmp;
        return SR_OK;
}

/**
 * Compose a string with a format string in the buffer pointed to by buf.
 *
 * It is up to the caller to ensure that the allocated buffer is large enough
 * to hold the formatted result.
 *
 * A terminating NUL character is automatically appended after the content
 * written.
 *
 * After the format parameter, the function expects at least as many additional
 * arguments as needed for format.
 *
 * This version ignores the current locale and uses the locale "C" for Linux,
 * FreeBSD, OSX and Android.
 *
 * @param buf Pointer to a buffer where the resulting C string is stored.
 * @param format C string that contains a format string (see printf).
 * @param ... A sequence of additional arguments, each containing a value to be
 *        used to replace a format specifier in the format string.
 *
 * @return On success, the number of characters that would have been written,
 *         not counting the terminating NUL character.
 *
 * @since 0.6.0
 */
SR_API int sr_sprintf_ascii(char *buf, const char *format, ...)
{
        int ret;
        va_list args;

        va_start(args, format);
        ret = sr_vsprintf_ascii(buf, format, args);
        va_end(args);

        return ret;
}

/**
 * Compose a string with a format string in the buffer pointed to by buf.
 *
 * It is up to the caller to ensure that the allocated buffer is large enough
 * to hold the formatted result.
 *
 * Internally, the function retrieves arguments from the list identified by
 * args as if va_arg was used on it, and thus the state of args is likely to
 * be altered by the call.
 *
 * In any case, args should have been initialized by va_start at some point
 * before the call, and it is expected to be released by va_end at some point
 * after the call.
 *
 * This version ignores the current locale and uses the locale "C" for Linux,
 * FreeBSD, OSX and Android.
 *
 * @param buf Pointer to a buffer where the resulting C string is stored.
 * @param format C string that contains a format string (see printf).
 * @param args A value identifying a variable arguments list initialized with
 *        va_start.
 *
 * @return On success, the number of characters that would have been written,
 *         not counting the terminating NUL character.
 *
 * @since 0.6.0
 */
SR_API int sr_vsprintf_ascii(char *buf, const char *format, va_list args)
{
#if defined(_WIN32)
        int ret;

#if 0
        /*
         * TODO: This part compiles with mingw-w64 but doesn't run with Win7.
         *       Doesn't start because of "Procedure entry point _create_locale
         *       not found in msvcrt.dll".
         *       mingw-w64 should link to msvcr100.dll not msvcrt.dll!
         * See: https://msdn.microsoft.com/en-us/en-en/library/1kt27hek.aspx
         */
        _locale_t locale;

        locale = _create_locale(LC_NUMERIC, "C");
        ret = _vsprintf_l(buf, format, locale, args);
        _free_locale(locale);
#endif

        /* vsprintf() uses the current locale, may not work correctly for floats. */
        ret = vsprintf(buf, format, args);

        return ret;
#elif defined(__APPLE__)
        /*
         * See:
         * https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man3/printf_l.3.html
         * https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man3/xlocale.3.html
         */
        int ret;
        locale_t locale;

        locale = newlocale(LC_NUMERIC_MASK, "C", NULL);
        ret = vsprintf_l(buf, locale, format, args);
        freelocale(locale);

        return ret;
#elif defined(__FreeBSD__) && __FreeBSD_version >= 901000
        /*
         * See:
         * https://www.freebsd.org/cgi/man.cgi?query=printf_l&apropos=0&sektion=3&manpath=FreeBSD+9.1-RELEASE
         * https://www.freebsd.org/cgi/man.cgi?query=xlocale&apropos=0&sektion=3&manpath=FreeBSD+9.1-RELEASE
         */
        int ret;
        locale_t locale;

        locale = newlocale(LC_NUMERIC_MASK, "C", NULL);
        ret = vsprintf_l(buf, locale, format, args);
        freelocale(locale);

        return ret;
#elif defined(__ANDROID__)
        /*
         * The Bionic libc only has two locales ("C" aka "POSIX" and "C.UTF-8"
         * aka "en_US.UTF-8"). The decimal point is hard coded as "."
         * See: https://android.googlesource.com/platform/bionic/+/master/libc/bionic/locale.cpp
         */
        int ret;

        ret = vsprintf(buf, format, args);

        return ret;
#elif defined(__linux__)
        int ret;
        locale_t old_locale, temp_locale;

        /* Switch to C locale for proper float/double conversion. */
        temp_locale = newlocale(LC_NUMERIC, "C", NULL);
        old_locale = uselocale(temp_locale);

        ret = vsprintf(buf, format, args);

        /* Switch back to original locale. */
        uselocale(old_locale);
        freelocale(temp_locale);

        return ret;
#elif defined(__unix__) || defined(__unix)
        /*
         * This is a fallback for all other BSDs, *nix and FreeBSD <= 9.0, by
         * using the current locale for snprintf(). This may not work correctly
         * for floats!
         */
        int ret;

        ret = vsprintf(buf, format, args);

        return ret;
#else
        /* No implementation for unknown systems! */
        return -1;
#endif
}

/**
 * Composes a string with a format string (like printf) in the buffer pointed
 * by buf (taking buf_size as the maximum buffer capacity to fill).
 * If the resulting string would be longer than n - 1 characters, the remaining
 * characters are discarded and not stored, but counted for the value returned
 * by the function.
 * A terminating NUL character is automatically appended after the content
 * written.
 * After the format parameter, the function expects at least as many additional
 * arguments as needed for format.
 *
 * This version ignores the current locale and uses the locale "C" for Linux,
 * FreeBSD, OSX and Android.
 *
 * @param buf Pointer to a buffer where the resulting C string is stored.
 * @param buf_size Maximum number of bytes to be used in the buffer. The
 *        generated string has a length of at most buf_size - 1, leaving space
 *        for the additional terminating NUL character.
 * @param format C string that contains a format string (see printf).
 * @param ... A sequence of additional arguments, each containing a value to be
 *        used to replace a format specifier in the format string.
 *
 * @return On success, the number of characters that would have been written if
 *         buf_size had been sufficiently large, not counting the terminating
 *         NUL character. On failure, a negative number is returned.
 *         Notice that only when this returned value is non-negative and less
 *         than buf_size, the string has been completely written.
 *
 * @since 0.6.0
 */
SR_API int sr_snprintf_ascii(char *buf, size_t buf_size,
        const char *format, ...)
{
        int ret;
        va_list args;

        va_start(args, format);
        ret = sr_vsnprintf_ascii(buf, buf_size, format, args);
        va_end(args);

        return ret;
}

/**
 * Composes a string with a format string (like printf) in the buffer pointed
 * by buf (taking buf_size as the maximum buffer capacity to fill).
 * If the resulting string would be longer than n - 1 characters, the remaining
 * characters are discarded and not stored, but counted for the value returned
 * by the function.
 * A terminating NUL character is automatically appended after the content
 * written.
 * Internally, the function retrieves arguments from the list identified by
 * args as if va_arg was used on it, and thus the state of args is likely to
 * be altered by the call.
 * In any case, arg should have been initialized by va_start at some point
 * before the call, and it is expected to be released by va_end at some point
 * after the call.
 *
 * This version ignores the current locale and uses the locale "C" for Linux,
 * FreeBSD, OSX and Android.
 *
 * @param buf Pointer to a buffer where the resulting C string is stored.
 * @param buf_size Maximum number of bytes to be used in the buffer. The
 *        generated string has a length of at most buf_size - 1, leaving space
 *        for the additional terminating NUL character.
 * @param format C string that contains a format string (see printf).
 * @param args A value identifying a variable arguments list initialized with
 *        va_start.
 *
 * @return On success, the number of characters that would have been written if
 *         buf_size had been sufficiently large, not counting the terminating
 *         NUL character. On failure, a negative number is returned.
 *         Notice that only when this returned value is non-negative and less
 *         than buf_size, the string has been completely written.
 *
 * @since 0.6.0
 */
SR_API int sr_vsnprintf_ascii(char *buf, size_t buf_size,
        const char *format, va_list args)
{
#if defined(_WIN32)
        int ret;

#if 0
        /*
         * TODO: This part compiles with mingw-w64 but doesn't run with Win7.
         *       Doesn't start because of "Procedure entry point _create_locale
         *       not found in msvcrt.dll".
         *       mingw-w64 should link to msvcr100.dll not msvcrt.dll!.
         * See: https://msdn.microsoft.com/en-us/en-en/library/1kt27hek.aspx
         */
        _locale_t locale;

        locale = _create_locale(LC_NUMERIC, "C");
        ret = _vsnprintf_l(buf, buf_size, format, locale, args);
        _free_locale(locale);
#endif

        /* vsprintf uses the current locale, may cause issues for floats. */
        ret = vsnprintf(buf, buf_size, format, args);

        return ret;
#elif defined(__APPLE__)
        /*
         * See:
         * https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man3/printf_l.3.html
         * https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man3/xlocale.3.html
         */
        int ret;
        locale_t locale;

        locale = newlocale(LC_NUMERIC_MASK, "C", NULL);
        ret = vsnprintf_l(buf, buf_size, locale, format, args);
        freelocale(locale);

        return ret;
#elif defined(__FreeBSD__) && __FreeBSD_version >= 901000
        /*
         * See:
         * https://www.freebsd.org/cgi/man.cgi?query=printf_l&apropos=0&sektion=3&manpath=FreeBSD+9.1-RELEASE
         * https://www.freebsd.org/cgi/man.cgi?query=xlocale&apropos=0&sektion=3&manpath=FreeBSD+9.1-RELEASE
         */
        int ret;
        locale_t locale;

        locale = newlocale(LC_NUMERIC_MASK, "C", NULL);
        ret = vsnprintf_l(buf, buf_size, locale, format, args);
        freelocale(locale);

        return ret;
#elif defined(__ANDROID__)
        /*
         * The Bionic libc only has two locales ("C" aka "POSIX" and "C.UTF-8"
         * aka "en_US.UTF-8"). The decimal point is hard coded as ".".
         * See: https://android.googlesource.com/platform/bionic/+/master/libc/bionic/locale.cpp
         */
        int ret;

        ret = vsnprintf(buf, buf_size, format, args);

        return ret;
#elif defined(__linux__)
        int ret;
        locale_t old_locale, temp_locale;

        /* Switch to C locale for proper float/double conversion. */
        temp_locale = newlocale(LC_NUMERIC, "C", NULL);
        old_locale = uselocale(temp_locale);

        ret = vsnprintf(buf, buf_size, format, args);

        /* Switch back to original locale. */
        uselocale(old_locale);
        freelocale(temp_locale);

        return ret;
#elif defined(__unix__) || defined(__unix)
        /*
         * This is a fallback for all other BSDs, *nix and FreeBSD <= 9.0, by
         * using the current locale for snprintf(). This may not work correctly
         * for floats!
         */
        int ret;

        ret = vsnprintf(buf, buf_size, format, args);

        return ret;
#else
        /* No implementation for unknown systems! */
        return -1;
#endif
}

/**
 * Convert a sequence of bytes to its textual representation ("hex dump").
 *
 * Callers should free the allocated GString. See sr_hexdump_free().
 *
 * @param[in] data Pointer to the byte sequence to print.
 * @param[in] len Number of bytes to print.
 *
 * @return NULL upon error, newly allocated GString pointer otherwise.
 *
 * @private
 */
SR_PRIV GString *sr_hexdump_new(const uint8_t *data, const size_t len)
{
        GString *s;
        size_t i;

        i = 3 * len;
        i += len / 8;
        i += len / 16;
        s = g_string_sized_new(i);
        for (i = 0; i < len; i++) {
                if (i)
                        g_string_append_c(s, ' ');
                if (i && (i % 8) == 0)
                        g_string_append_c(s, ' ');
                if (i && (i % 16) == 0)
                        g_string_append_c(s, ' ');
                g_string_append_printf(s, "%02x", data[i]);
        }

        return s;
}

/**
 * Free a hex dump text that was created by sr_hexdump_new().
 *
 * @param[in] s Pointer to the GString to release.
 *
 * @private
 */
SR_PRIV void sr_hexdump_free(GString *s)
{
        if (s)
                g_string_free(s, TRUE);
}

/**
 * Convert a string representation of a numeric value to a sr_rational.
 *
 * The conversion is strict and will fail if the complete string does not
 * represent a valid number. The function sets errno according to the details
 * of the failure. This version ignores the locale.
 *
 * @param str The string representation to convert.
 * @param ret Pointer to sr_rational where the result of the conversion will be stored.
 *
 * @retval SR_OK Conversion successful.
 * @retval SR_ERR Failure.
 *
 * @since 0.5.0
 */
SR_API int sr_parse_rational(const char *str, struct sr_rational *ret)
{
        const char *readptr;
        char *endptr;
        gboolean is_negative, empty_integral, empty_fractional, exp_negative;
        int64_t integral;
        int64_t fractional;
        int64_t denominator;
        uint32_t fractional_len;
        int32_t exponent;

        /*
         * Implementor's note: This routine tries hard to avoid calling
         * glib's or the platform's conversion routines with input that
         * cannot get converted *at all* (see bug #1093). It also takes
         * care to return with non-zero errno values for any failed
         * conversion attempt. It's assumed that correctness and robustness
         * are more important than performance, which is why code paths
         * are not optimized at all. Maintainability took priority.
         */

        readptr = str;

        /* Skip leading whitespace. */
        while (isspace(*readptr))
                readptr++;

        /* Determine the sign, default to non-negative. */
        is_negative = FALSE;
        if (*readptr == '-') {
                is_negative = TRUE;
                readptr++;
        } else if (*readptr == '+') {
                is_negative = FALSE;
                readptr++;
        }

        /* Get the (optional) integral part. */
        empty_integral = TRUE;
        integral = 0;
        endptr = (char *)readptr;
        errno = 0;
        if (isdigit(*readptr)) {
                empty_integral = FALSE;
                integral = g_ascii_strtoll(readptr, &endptr, 10);
                if (errno)
                        return SR_ERR;
                if (endptr == str) {
                        errno = -EINVAL;
                        return SR_ERR;
                }
                readptr = endptr;
        }

        /* Get the optional fractional part. */
        empty_fractional = TRUE;
        fractional = 0;
        fractional_len = 0;
        if (*readptr == '.') {
                readptr++;
                endptr++;
                errno = 0;
                if (isdigit(*readptr)) {
                        empty_fractional = FALSE;
                        fractional = g_ascii_strtoll(readptr, &endptr, 10);
                        if (errno)
                                return SR_ERR;
                        if (endptr == readptr) {
                                errno = -EINVAL;
                                return SR_ERR;
                        }
                        fractional_len = endptr - readptr;
                        readptr = endptr;
                }
        }

        /* At least one of integral or fractional is required. */
        if (empty_integral && empty_fractional) {
                errno = -EINVAL;
                return SR_ERR;
        }

        /* Get the (optional) exponent. */
        exponent = 0;
        if ((*readptr == 'E') || (*readptr == 'e')) {
                readptr++;
                endptr++;
                exp_negative = FALSE;
                if (*readptr == '+') {
                        exp_negative = FALSE;
                        readptr++;
                        endptr++;
                } else if (*readptr == '-') {
                        exp_negative = TRUE;
                        readptr++;
                        endptr++;
                }
                if (!isdigit(*readptr)) {
                        errno = -EINVAL;
                        return SR_ERR;
                }
                errno = 0;
                exponent = g_ascii_strtoll(readptr, &endptr, 10);
                if (errno)
                        return SR_ERR;
                if (endptr == readptr) {
                        errno = -EINVAL;
                        return SR_ERR;
                }
                readptr = endptr;
                if (exp_negative)
                        exponent = -exponent;
        }

        /* Input must be exhausted. Unconverted remaining input is fatal. */
        if (*endptr != '\0') {
                errno = -EINVAL;
                return SR_ERR;
        }

        /*
         * Apply the sign to the integral (and fractional) part(s).
         * Adjust exponent (decimal position) such that the above integral
         * and fractional parts both fit into the (new) integral part.
         */
        if (is_negative)
                integral = -integral;
        while (fractional_len-- > 0) {
                integral *= 10;
                exponent--;
        }
        if (!is_negative)
                integral += fractional;
        else
                integral -= fractional;
        while (exponent > 0) {
                integral *= 10;
                exponent--;
        }

        /*
         * When significant digits remain after the decimal, scale up the
         * denominator such that we end up with two integer p/q numbers.
         */
        denominator = 1;
        while (exponent < 0) {
                denominator *= 10;
                exponent++;
        }

        ret->p = integral;
        ret->q = denominator;

        return SR_OK;
}

/**
 * Convert a numeric value value to its "natural" string representation
 * in SI units.
 *
 * E.g. a value of 3000000, with units set to "W", would be converted
 * to "3 MW", 20000 to "20 kW", 31500 would become "31.5 kW".
 *
 * @param x The value to convert.
 * @param unit The unit to append to the string, or NULL if the string
 *             has no units.
 *
 * @return A newly allocated string representation of the samplerate value,
 *         or NULL upon errors. The caller is responsible to g_free() the
 *         memory.
 *
 * @since 0.2.0
 */
SR_API char *sr_si_string_u64(uint64_t x, const char *unit)
{
        uint8_t i;
        uint64_t quot, divisor[] = {
                SR_HZ(1), SR_KHZ(1), SR_MHZ(1), SR_GHZ(1),
                SR_GHZ(1000), SR_GHZ(1000 * 1000), SR_GHZ(1000 * 1000 * 1000),
        };
        const char *p, prefix[] = "\0kMGTPE";
        char fmt[16], fract[20] = "", *f;

        if (!unit)
                unit = "";

        for (i = 0; (quot = x / divisor[i]) >= 1000; i++);

        if (i) {
                sprintf(fmt, ".%%0%d"PRIu64, i * 3);
                f = fract + sprintf(fract, fmt, x % divisor[i]) - 1;

                while (f >= fract && strchr("0.", *f))
                        *f-- = 0;
        }

        p = prefix + i;

        return g_strdup_printf("%" PRIu64 "%s %.1s%s", quot, fract, p, unit);
}

/**
 * Convert a numeric samplerate value to its "natural" string representation.
 *
 * E.g. a value of 3000000 would be converted to "3 MHz", 20000 to "20 kHz",
 * 31500 would become "31.5 kHz".
 *
 * @param samplerate The samplerate in Hz.
 *
 * @return A newly allocated string representation of the samplerate value,
 *         or NULL upon errors. The caller is responsible to g_free() the
 *         memory.
 *
 * @since 0.1.0
 */
SR_API char *sr_samplerate_string(uint64_t samplerate)
{
        return sr_si_string_u64(samplerate, "Hz");
}

/**
 * Convert a numeric period value to the "natural" string representation
 * of its period value.
 *
 * The period is specified as a rational number's numerator and denominator.
 *
 * E.g. a pair of (1, 5) would be converted to "200 ms", (10, 100) to "100 ms".
 *
 * @param v_p The period numerator.
 * @param v_q The period denominator.
 *
 * @return A newly allocated string representation of the period value,
 *         or NULL upon errors. The caller is responsible to g_free() the
 *         memory.
 *
 * @since 0.5.0
 */
SR_API char *sr_period_string(uint64_t v_p, uint64_t v_q)
{
        double freq, v;
        int prec;

        freq = 1 / ((double)v_p / v_q);

        if (freq > SR_GHZ(1)) {
                v = (double)v_p / v_q * 1000000000000.0;
                prec = ((v - (uint64_t)v) < FLT_MIN) ? 0 : 3;
                return g_strdup_printf("%.*f ps", prec, v);
        } else if (freq > SR_MHZ(1)) {
                v = (double)v_p / v_q * 1000000000.0;
                prec = ((v - (uint64_t)v) < FLT_MIN) ? 0 : 3;
                return g_strdup_printf("%.*f ns", prec, v);
        } else if (freq > SR_KHZ(1)) {
                v = (double)v_p / v_q * 1000000.0;
                prec = ((v - (uint64_t)v) < FLT_MIN) ? 0 : 3;
                return g_strdup_printf("%.*f us", prec, v);
        } else if (freq > 1) {
                v = (double)v_p / v_q * 1000.0;
                prec = ((v - (uint64_t)v) < FLT_MIN) ? 0 : 3;
                return g_strdup_printf("%.*f ms", prec, v);
        } else {
                v = (double)v_p / v_q;
                prec = ((v - (uint64_t)v) < FLT_MIN) ? 0 : 3;
                return g_strdup_printf("%.*f s", prec, v);
        }
}

/**
 * Convert a numeric voltage value to the "natural" string representation
 * of its voltage value. The voltage is specified as a rational number's
 * numerator and denominator.
 *
 * E.g. a value of 300000 would be converted to "300mV", 2 to "2V".
 *
 * @param v_p The voltage numerator.
 * @param v_q The voltage denominator.
 *
 * @return A newly allocated string representation of the voltage value,
 *         or NULL upon errors. The caller is responsible to g_free() the
 *         memory.
 *
 * @since 0.2.0
 */
SR_API char *sr_voltage_string(uint64_t v_p, uint64_t v_q)
{
        if (v_q == 1000)
                return g_strdup_printf("%" PRIu64 " mV", v_p);
        else if (v_q == 1)
                return g_strdup_printf("%" PRIu64 " V", v_p);
        else
                return g_strdup_printf("%g V", (float)v_p / (float)v_q);
}

/**
 * Convert a "natural" string representation of a size value to uint64_t.
 *
 * E.g. a value of "3k" or "3 K" would be converted to 3000, a value
 * of "15M" would be converted to 15000000.
 *
 * Value representations other than decimal (such as hex or octal) are not
 * supported. Only 'k' (kilo), 'm' (mega), 'g' (giga) suffixes are supported.
 * Spaces (but not other whitespace) between value and suffix are allowed.
 *
 * @param sizestring A string containing a (decimal) size value.
 * @param size Pointer to uint64_t which will contain the string's size value.
 *
 * @return SR_OK upon success, SR_ERR upon errors.
 *
 * @since 0.1.0
 */
SR_API int sr_parse_sizestring(const char *sizestring, uint64_t *size)
{
        uint64_t multiplier;
        int done;
        double frac_part;
        char *s;

        *size = strtoull(sizestring, &s, 10);
        multiplier = 0;
        frac_part = 0;
        done = FALSE;
        while (s && *s && multiplier == 0 && !done) {
                switch (*s) {
                case ' ':
                        break;
                case '.':
                        frac_part = g_ascii_strtod(s, &s);
                        break;
                case 'k':
                case 'K':
                        multiplier = SR_KHZ(1);
                        break;
                case 'm':
                case 'M':
                        multiplier = SR_MHZ(1);
                        break;
                case 'g':
                case 'G':
                        multiplier = SR_GHZ(1);
                        break;
                case 't':
                case 'T':
                        multiplier = SR_GHZ(1000);
                        break;
                case 'p':
                case 'P':
                        multiplier = SR_GHZ(1000 * 1000);
                        break;
                case 'e':
                case 'E':
                        multiplier = SR_GHZ(1000 * 1000 * 1000);
                        break;
                default:
                        done = TRUE;
                        s--;
                }
                s++;
        }
        if (multiplier > 0) {
                *size *= multiplier;
                *size += frac_part * multiplier;
        } else {
                *size += frac_part;
        }

        if (s && *s && g_ascii_strcasecmp(s, "Hz"))
                return SR_ERR;

        return SR_OK;
}

/**
 * Convert a "natural" string representation of a time value to an
 * uint64_t value in milliseconds.
 *
 * E.g. a value of "3s" or "3 s" would be converted to 3000, a value
 * of "15ms" would be converted to 15.
 *
 * Value representations other than decimal (such as hex or octal) are not
 * supported. Only lower-case "s" and "ms" time suffixes are supported.
 * Spaces (but not other whitespace) between value and suffix are allowed.
 *
 * @param timestring A string containing a (decimal) time value.
 * @return The string's time value as uint64_t, in milliseconds.
 *
 * @todo Add support for "m" (minutes) and others.
 * @todo Add support for picoseconds?
 * @todo Allow both lower-case and upper-case? If no, document it.
 *
 * @since 0.1.0
 */
SR_API uint64_t sr_parse_timestring(const char *timestring)
{
        uint64_t time_msec;
        char *s;

        /* TODO: Error handling, logging. */

        time_msec = strtoull(timestring, &s, 10);
        if (time_msec == 0 && s == timestring)
                return 0;

        if (s && *s) {
                while (*s == ' ')
                        s++;
                if (!strcmp(s, "s"))
                        time_msec *= 1000;
                else if (!strcmp(s, "ms"))
                        ; /* redundant */
                else
                        return 0;
        }

        return time_msec;
}

/** @since 0.1.0 */
SR_API gboolean sr_parse_boolstring(const char *boolstr)
{
        /*
         * Complete absence of an input spec is assumed to mean TRUE,
         * as in command line option strings like this:
         *   ...:samplerate=100k:header:numchannels=4:...
         */
        if (!boolstr || !*boolstr)
                return TRUE;

        if (!g_ascii_strncasecmp(boolstr, "true", 4) ||
            !g_ascii_strncasecmp(boolstr, "yes", 3) ||
            !g_ascii_strncasecmp(boolstr, "on", 2) ||
            !g_ascii_strncasecmp(boolstr, "1", 1))
                return TRUE;

        return FALSE;
}

/** @since 0.2.0 */
SR_API int sr_parse_period(const char *periodstr, uint64_t *p, uint64_t *q)
{
        char *s;

        *p = strtoull(periodstr, &s, 10);
        if (*p == 0 && s == periodstr)
                /* No digits found. */
                return SR_ERR_ARG;

        if (s && *s) {
                while (*s == ' ')
                        s++;
                if (!strcmp(s, "fs"))
                        *q = UINT64_C(1000000000000000);
                else if (!strcmp(s, "ps"))
                        *q = UINT64_C(1000000000000);
                else if (!strcmp(s, "ns"))
                        *q = UINT64_C(1000000000);
                else if (!strcmp(s, "us"))
                        *q = 1000000;
                else if (!strcmp(s, "ms"))
                        *q = 1000;
                else if (!strcmp(s, "s"))
                        *q = 1;
                else
                        /* Must have a time suffix. */
                        return SR_ERR_ARG;
        }

        return SR_OK;
}

/** @since 0.2.0 */
SR_API int sr_parse_voltage(const char *voltstr, uint64_t *p, uint64_t *q)
{
        char *s;

        *p = strtoull(voltstr, &s, 10);
        if (*p == 0 && s == voltstr)
                /* No digits found. */
                return SR_ERR_ARG;

        if (s && *s) {
                while (*s == ' ')
                        s++;
                if (!g_ascii_strcasecmp(s, "mv"))
                        *q = 1000L;
                else if (!g_ascii_strcasecmp(s, "v"))
                        *q = 1;
                else
                        /* Must have a base suffix. */
                        return SR_ERR_ARG;
        }

        return SR_OK;
}

/**
 * Append another text item to a NULL terminated string vector.
 *
 * @param[in] table The previous string vector.
 * @param[in,out] sz The previous and the resulting vector size
 *       (item count).
 * @param[in] text The text string to append to the vector.
 *       Can be #NULL.
 *
 * @returns The new vector, its location can differ from 'table'.
 *       Or #NULL in case of failure.
 *
 * This implementation happens to work for the first invocation when
 * 'table' is #NULL and 'sz' is 0, as well as subsequent append calls.
 * The 'text' can be #NULL or can be a non-empty string. When 'sz' is
 * not provided, then the 'table' must be a NULL terminated vector,
 * so that the routine can auto-determine the vector's current length.
 *
 * This routine re-allocates the vector as needed. Callers must not
 * rely on the memory address to remain the same across calls.
 */
static char **append_probe_name(char **table, size_t *sz, const char *text)
{
        size_t curr_size, alloc_size;
        char **new_table;

        /* Get the table's previous size (item count). */
        if (sz)
                curr_size = *sz;
        else if (table)
                curr_size = g_strv_length(table);
        else
                curr_size = 0;

        /* Extend storage to hold one more item, and the termination. */
        alloc_size = curr_size + (text ? 1 : 0) + 1;
        alloc_size *= sizeof(table[0]);
        new_table = g_realloc(table, alloc_size);
        if (!new_table) {
                g_strfreev(table);
                if (sz)
                        *sz = 0;
                return NULL;
        }

        /* Append the item, NULL terminate. */
        if (text) {
                new_table[curr_size] = g_strdup(text);
                if (!new_table[curr_size]) {
                        g_strfreev(new_table);
                        if (sz)
                                *sz = 0;
                        return NULL;
                }
                curr_size++;
        }
        if (sz)
                *sz = curr_size;
        new_table[curr_size] = NULL;

        return new_table;
}

static char **append_probe_names(char **table, size_t *sz,
        const char **names)
{
        if (!names)
                return table;

        while (names[0]) {
                table = append_probe_name(table, sz, names[0]);
                names++;
        }
        return table;
}

static const struct {
        const char *name;
        const char **expands;
} probe_name_aliases[] = {
        {
                "ac97", (const char *[]){
                        "sync", "clk",
                        "out", "in", "rst",
                        NULL,
                },
        },
        {
                "i2c", (const char *[]){
                        "scl", "sda", NULL,
                },
        },
        {
                "jtag", (const char *[]){
                        "tdi", "tdo", "tck", "tms", NULL,
                },
        },
        {
                "jtag-opt", (const char *[]){
                        "tdi", "tdo", "tck", "tms",
                        "trst", "srst", "rtck", NULL,
                },
        },
        {
                "ieee488", (const char *[]){
                        "dio1", "dio2", "dio3", "dio4",
                        "dio5", "dio6", "dio7", "dio8",
                        "eoi", "dav", "nrfd", "ndac",
                        "ifc", "srq", "atn", "ren", NULL,
                },
        },
        {
                "lpc", (const char *[]){
                        "lframe", "lclk",
                        "lad0", "lad1", "lad2", "lad3",
                        NULL,
                },
        },
        {
                "lpc-opt", (const char *[]){
                        "lframe", "lclk",
                        "lad0", "lad1", "lad2", "lad3",
                        "lreset", "ldrq", "serirq", "clkrun",
                        "lpme", "lpcpd", "lsmi",
                        NULL,
                },
        },
        {
                "mcs48", (const char *[]){
                        "ale", "psen",
                        "d0", "d1", "d2", "d3",
                        "d4", "d5", "d6", "d7",
                        "a8", "a9", "a10", "a11",
                        "a12", "a13",
                        NULL,
                },
        },
        {
                "microwire", (const char *[]){
                        "cs", "sk", "si", "so", NULL,
                },
        },
        {
                "sdcard_sd", (const char *[]){
                        "cmd", "clk",
                        "dat0", "dat1", "dat2", "dat3",
                        NULL,
                },
        },
        {
                "seven_segment", (const char *[]){
                        "a", "b", "c", "d", "e", "f", "g",
                        "dp", NULL,
                },
        },
        {
                "spi", (const char *[]){
                        "clk", "miso", "mosi", "cs", NULL,
                },
        },
        {
                "swd", (const char *[]){
                        "swclk", "swdio", NULL,
                },
        },
        {
                "uart", (const char *[]){
                        "rx", "tx", NULL,
                },
        },
        {
                "usb", (const char *[]){
                        "dp", "dm", NULL,
                },
        },
        {
                "z80", (const char *[]){
                        "d0", "d1", "d2", "d3",
                        "d4", "d5", "d6", "d7",
                        "m1", "rd", "wr",
                        "mreq", "iorq",
                        "a0", "a1", "a2", "a3",
                        "a4", "a5", "a6", "a7",
                        "a8", "a9", "a10", "a11",
                        "a12", "a13", "a14", "a15",
                        NULL,
                },
        },
};

/* Case insensitive lookup of an alias name. */
static const char **lookup_probe_alias(const char *name)
{
        size_t idx;

        for (idx = 0; idx < ARRAY_SIZE(probe_name_aliases); idx++) {
                if (g_ascii_strcasecmp(probe_name_aliases[idx].name, name) != 0)
                        continue;
                return probe_name_aliases[idx].expands;
        }
        return NULL;
}

/**
 * Parse a probe names specification, allocate a string vector.
 *
 * @param[in] spec The input spec, list of probes or aliases.
 * @param[in] dflt_names The default probe names, a string array.
 * @param[in] dflt_count The default probe names count. Either must
 *        match the unterminated array size, or can be 0 when the
 *        default names are NULL terminated.
 * @param[in] max_count Optional resulting vector size limit.
 * @param[out] ret_count Optional result vector size (return value).
 *
 * @returns A string vector with resulting probe names. Or #NULL
 *        in case of failure.
 *
 * The input spec is a comma separated list of probe names. Items can
 * be aliases which expand to a corresponding set of signal names.
 * The resulting names list optionally gets padded from the caller's
 * builtin probe names, an empty input spec yields the original names
 * as provided by the caller. Padding is omitted when the spec starts
 * with '-', which may result in a device with fewer channels being
 * created, enough to cover the user's spec, but none extra to maybe
 * enable and use later on. An optional maximum length spec will trim
 * the result set to that size. The resulting vector length optionally
 * is returned to the caller, so that it need not re-get the length.
 *
 * Calling applications must release the allocated vector by means
 * of @ref sr_free_probe_names().
 *
 * @since 0.6.0
 */
SR_API char **sr_parse_probe_names(const char *spec,
        const char **dflt_names, size_t dflt_count,
        size_t max_count, size_t *ret_count)
{
        char **result_names;
        size_t result_count;
        gboolean pad_from_dflt;
        char **spec_names, *spec_name;
        size_t spec_idx;
        const char **alias_names;

        if (!spec || !*spec)
                spec = NULL;

        /*
         * Accept zero length spec for default input names. Determine
         * the name table's length here. Cannot re-use g_strv_length()
         * because of the 'const' decoration in application code.
         */
        if (!dflt_count) {
                while (dflt_names && dflt_names[dflt_count])
                        dflt_count++;
        }
        if (!dflt_count)
                return NULL;

        /*
         * Start with an empty resulting names table. Will grow
         * dynamically as more names get appended.
         */
        result_names = NULL;
        result_count = 0;
        pad_from_dflt = TRUE;

        /*
         * When an input spec exists, use its content. Lookup alias
         * names, and append their corresponding signals. Or append
         * the verbatim input name if it is not an alias. Recursion
         * is not supported in this implementation.
         *
         * A leading '-' before the signal names list suppresses the
         * padding of the resulting list from the device's default
         * probe names.
         */
        spec_names = NULL;
        if (spec && *spec == '-') {
                spec++;
                pad_from_dflt = FALSE;
        }
        if (spec && *spec)
                spec_names = g_strsplit(spec, ",", 0);
        for (spec_idx = 0; spec_names && spec_names[spec_idx]; spec_idx++) {
                spec_name = spec_names[spec_idx];
                if (!*spec_name)
                        continue;
                alias_names = lookup_probe_alias(spec_name);
                if (alias_names) {
                        result_names = append_probe_names(result_names,
                                &result_count, alias_names);
                } else {
                        result_names = append_probe_name(result_names,
                                &result_count, spec_name);
                }
        }
        g_strfreev(spec_names);

        /*
         * By default pad the resulting names from the caller's
         * probe names. Don't pad if the input spec started with
         * '-', when the spec's exact length was requested.
         */
        if (pad_from_dflt) do {
                if (max_count && result_count >= max_count)
                        break;
                if (result_count >= dflt_count)
                        break;
                result_names = append_probe_name(result_names, &result_count,
                        dflt_names[result_count]);
        } while (1);

        /* Optionally trim the result to the caller's length limit. */
        if (max_count) {
                while (result_count > max_count) {
                        --result_count;
                        g_free(result_names[result_count]);
                        result_names[result_count] = NULL;
                }
        }

        if (ret_count)
                *ret_count = result_count;

        return result_names;
}

/**
 * Release previously allocated probe names (string vector).
 *
 * @param[in] names The previously allocated string vector.
 *
 * @since 0.6.0
 */
SR_API void sr_free_probe_names(char **names)
{
        g_strfreev(names);
}

/**
 * Trim leading and trailing whitespace off text.
 *
 * @param[in] s The input text.
 *
 * @return Start of trimmed input text.
 *
 * Manipulates the caller's input text in place.
 *
 * @since 0.6.0
 */
SR_API char *sr_text_trim_spaces(char *s)
{
        char *p;

        if (!s || !*s)
                return s;

        p = s + strlen(s);
        while (p > s && isspace((int)p[-1]))
                *(--p) = '\0';
        while (isspace((int)*s))
                s++;

        return s;
}

/**
 * Check for another complete text line, trim, return consumed char count.
 *
 * @param[in] s The input text, current read position.
 * @param[in] l The input text, remaining available characters.
 * @param[out] next Position after the current text line.
 * @param[out] taken Count of consumed chars in current text line.
 *
 * @return Start of trimmed and NUL terminated text line.
 *   Or #NULL when no text line was found.
 *
 * Checks for the availability of another text line of input data.
 * Manipulates the caller's input text in place.
 *
 * The end-of-line condition is the LF character ('\n'). Which covers
 * LF-only as well as CR/LF input data. CR-only and LF/CR are considered
 * unpopular and are not supported. LF/CR may appear to work at the
 * caller's when leading whitespace gets trimmed (line boundaries will
 * be incorrect, but content may get processed as expected). Support for
 * all of the above combinations breaks the detection of empty lines (or
 * becomes unmaintainably complex).
 *
 * The input buffer must be end-of-line terminated, lack of EOL results
 * in failure to detect the text line. This is motivated by accumulating
 * input in chunks, and the desire to not process incomplete lines before
 * their reception has completed. Callers should enforce EOL if their
 * source of input provides an EOF condition and is unreliable in terms
 * of text line termination.
 *
 * When another text line is available, it gets NUL terminated and
 * space gets trimmed of both ends. The start position of the trimmed
 * text line is returned. Optionally the number of consumed characters
 * is returned to the caller. Optionally 'next' points to after the
 * returned text line, or #NULL when no other text is available in the
 * input buffer.
 *
 * The 'taken' value is not preset by this routine, only gets updated.
 * This is convenient for callers which expect to find multiple text
 * lines in a received chunk, before finally discarding processed data
 * from the input buffer (which can involve expensive memory move
 * operations, and may be desirable to defer as much as possible).
 *
 * @since 0.6.0
 */
SR_API char *sr_text_next_line(char *s, size_t l, char **next, size_t *taken)
{
        char *p;

        if (next)
                *next = NULL;
        if (!l)
                l = strlen(s);

        /* Immediate reject incomplete input data. */
        if (!s || !*s || !l)
                return NULL;

        /* Search for the next line termination. NUL terminate. */
        p = g_strstr_len(s, l, "\n");
        if (!p)
                return NULL;
        *p++ = '\0';
        if (taken)
                *taken += p - s;
        l -= p - s;
        if (next)
                *next = l ? p : NULL;

        /* Trim NUL terminated text line at both ends. */
        s = sr_text_trim_spaces(s);
        return s;
}

/**
 * Isolates another space separated word in a text line.
 *
 * @param[in] s The input text, current read position.
 * @param[out] next The position after the current word.
 *
 * @return The start of the current word. Or #NULL if there is none.
 *
 * Advances over leading whitespace. Isolates (NUL terminates) the next
 * whitespace separated word. Optionally returns the position after the
 * current word. Manipulates the caller's input text in place.
 *
 * @since 0.6.0
 */
SR_API char *sr_text_next_word(char *s, char **next)
{
        char *word, *p;

        word = s;
        if (next)
                *next = NULL;

        /* Immediately reject incomplete input data. */
        if (!word || !*word)
                return NULL;

        /* Advance over optional leading whitespace. */
        while (isspace((int)*word))
                word++;
        if (!*word)
                return NULL;

        /*
         * Advance until whitespace or end of text. Quick return when
         * end of input is seen. Otherwise advance over whitespace and
         * return the position of trailing text.
         */
        p = word;
        while (*p && !isspace((int)*p))
                p++;
        if (!*p)
                return word;
        *p++ = '\0';
        while (isspace((int)*p))
                p++;
        if (!*p)
                return word;
        if (next)
                *next = p;
        return word;
}

/**
 * Get the number of necessary bits to hold a given value. Also gets
 * the next power-of-two value at or above the caller provided value.
 *
 * @param[in] value The value that must get stored.
 * @param[out] bits The required number of bits.
 * @param[out] power The corresponding power-of-two.
 *
 * @return SR_OK upon success, SR_ERR* otherwise.
 *
 * TODO Move this routine to a more appropriate location, it is not
 * strictly string related.
 *
 * @since 0.6.0
 */
SR_API int sr_next_power_of_two(size_t value, size_t *bits, size_t *power)
{
        size_t need_bits;
        size_t check_mask;

        if (bits)
                *bits = 0;
        if (power)
                *power = 0;

        /*
         * Handle the special case of input value 0 (needs 1 bit
         * and results in "power of two" value 1) here. It is not
         * covered by the generic logic below.
         */
        if (!value) {
                if (bits)
                        *bits = 1;
                if (power)
                        *power = 1;
                return SR_OK;
        }

        need_bits = 0;
        check_mask = 0;
        do {
                need_bits++;
                check_mask <<= 1;
                check_mask |= 1UL << 0;
        } while (value & ~check_mask);

        if (bits)
                *bits = need_bits;
        if (power)
                *power = ++check_mask;
        return SR_OK;
}

/** @} */