resource.c

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/*
 * This file is part of the libsigrok project.
 *
 * Copyright (C) 2015 Daniel Elstner <daniel.kitta@gmail.com>
 *
 * 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 3 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/>.
 */

#include <config.h>
#include <errno.h>
#include <stdio.h>
#include <glib.h>
#include <glib/gstdio.h>
#include <libsigrok/libsigrok.h>
#include "libsigrok-internal.h"

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

/**
 * @file
 *
 * Access to resource files.
 */

/** Retrieve the size of the open stream @a file.
 *
 * This function only works on seekable streams. However, the set of seekable
 * streams is generally congruent with the set of streams that have a size.
 * Code that needs to work with any type of stream (including pipes) should
 * require neither seekability nor advance knowledge of the size.
 * On failure, the return value is negative and errno is set.
 *
 * @param file An I/O stream opened in binary mode.
 * @return The size of @a file in bytes, or a negative value on failure.
 *
 * @private
 */
SR_PRIV int64_t sr_file_get_size(FILE *file)
{
        off_t filepos, filesize;

        /* ftello() and fseeko() are not standard C, but part of POSIX.1-2001.
         * Thus, if these functions are available at all, they can reasonably
         * be expected to also conform to POSIX semantics. In particular, this
         * means that ftello() after fseeko(..., SEEK_END) has a defined result
         * and can be used to get the size of a seekable stream.
         * On Windows, the result is fully defined only for binary streams.
         */
        filepos = ftello(file);
        if (filepos < 0)
                return -1;

        if (fseeko(file, 0, SEEK_END) < 0)
                return -1;

        filesize = ftello(file);
        if (filesize < 0)
                return -1;

        if (fseeko(file, filepos, SEEK_SET) < 0)
                return -1;

        return filesize;
}

static FILE *try_open_file(const char *datadir, const char *subdir,
                const char *name)
{
        char *filename;
        FILE *file;

        filename = g_build_filename(datadir, subdir, name, NULL);
        file = g_fopen(filename, "rb");

        if (file)
                sr_info("Opened '%s'.", filename);
        else
                sr_spew("Attempt to open '%s' failed: %s",
                        filename, g_strerror(errno));
        g_free(filename);

        return file;
}

static int resource_open_default(struct sr_resource *res,
                const char *name, void *cb_data)
{
        int64_t filesize;
#ifdef FIRMWARE_DIR
        const char *builtindir;
#endif
        const char *subdir;
        const char *const *datadirs;
        FILE *file;

        (void)cb_data;

        switch (res->type) {
        case SR_RESOURCE_FIRMWARE:
#ifdef FIRMWARE_DIR
                builtindir = FIRMWARE_DIR;
#endif
                subdir = "sigrok-firmware";
                break;
        default:
                sr_err("%s: unknown type %d.", __func__, res->type);
                return SR_ERR_ARG;
        }

        file = try_open_file(g_get_user_data_dir(), subdir, name);
        /*
         * Scan the hard-coded directory before the system directories to
         * avoid picking up possibly outdated files from a system install.
         */
#ifdef FIRMWARE_DIR
        if (!file)
                file = try_open_file(builtindir, "", name);
#endif
        if (!file) {
                datadirs = g_get_system_data_dirs();
                while (*datadirs && !file)
                        file = try_open_file(*datadirs++, subdir, name);
        }
        if (!file) {
                sr_err("Failed to locate '%s'.", name);
                return SR_ERR;
        }

        filesize = sr_file_get_size(file);
        if (filesize < 0) {
                sr_err("Failed to obtain size of '%s': %s",
                        name, g_strerror(errno));
                fclose(file);
                return SR_ERR;
        }
        res->size = filesize;
        res->handle = file;

        return SR_OK;
}

static int resource_close_default(struct sr_resource *res, void *cb_data)
{
        FILE *file;

        (void)cb_data;

        file = res->handle;
        if (!file) {
                sr_err("%s: invalid handle.", __func__);
                return SR_ERR_ARG;
        }

        if (fclose(file) < 0) {
                sr_err("Failed to close file: %s", g_strerror(errno));
                return SR_ERR;
        }
        res->handle = NULL;

        return SR_OK;
}

static gssize resource_read_default(const struct sr_resource *res,
                void *buf, size_t count, void *cb_data)
{
        FILE *file;
        size_t n_read;

        (void)cb_data;

        file = res->handle;
        if (!file) {
                sr_err("%s: invalid handle.", __func__);
                return SR_ERR_ARG;
        }
        if (count > G_MAXSSIZE) {
                sr_err("%s: count %zu too large.", __func__, count);
                return SR_ERR_ARG;
        }

        n_read = fread(buf, 1, count, file);

        if (n_read != count && ferror(file)) {
                sr_err("Failed to read resource file: %s", g_strerror(errno));
                return SR_ERR;
        }
        return n_read;
}

/**
 * Install resource access hooks.
 *
 * @param ctx libsigrok context. Must not be NULL.
 * @param open_cb Resource open callback, or NULL to unset.
 * @param close_cb Resource close callback, or NULL to unset.
 * @param read_cb Resource read callback, or NULL to unset.
 * @param cb_data User data pointer passed to callbacks.
 *
 * @retval SR_OK Success.
 * @retval SR_ERR_ARG Invalid argument.
 *
 * @since 0.4.0
 */
SR_API int sr_resource_set_hooks(struct sr_context *ctx,
                sr_resource_open_callback open_cb,
                sr_resource_close_callback close_cb,
                sr_resource_read_callback read_cb, void *cb_data)
{
        if (!ctx) {
                sr_err("%s: ctx was NULL.", __func__);
                return SR_ERR_ARG;
        }
        if (open_cb && close_cb && read_cb) {
                ctx->resource_open_cb  = open_cb;
                ctx->resource_close_cb = close_cb;
                ctx->resource_read_cb  = read_cb;
                ctx->resource_cb_data  = cb_data;
        } else if (!open_cb && !close_cb && !read_cb) {
                ctx->resource_open_cb  = &resource_open_default;
                ctx->resource_close_cb = &resource_close_default;
                ctx->resource_read_cb  = &resource_read_default;
                ctx->resource_cb_data  = ctx;
        } else {
                sr_err("%s: inconsistent callback pointers.", __func__);
                return SR_ERR_ARG;
        }
        return SR_OK;
}

/**
 * Open resource.
 *
 * @param ctx libsigrok context. Must not be NULL.
 * @param[out] res Resource descriptor to fill in. Must not be NULL.
 * @param type Resource type ID.
 * @param name Name of the resource. Must not be NULL.
 *
 * @retval SR_OK Success.
 * @retval SR_ERR_ARG Invalid argument.
 * @retval SR_ERR Other error.
 *
 * @private
 */
SR_PRIV int sr_resource_open(struct sr_context *ctx,
                struct sr_resource *res, int type, const char *name)
{
        int ret;

        res->size = 0;
        res->handle = NULL;
        res->type = type;

        ret = (*ctx->resource_open_cb)(res, name, ctx->resource_cb_data);

        if (ret != SR_OK)
                sr_err("Failed to open resource '%s'.", name);

        return ret;
}

/**
 * Close resource.
 *
 * @param ctx libsigrok context. Must not be NULL.
 * @param[inout] res Resource descriptor. Must not be NULL.
 *
 * @retval SR_OK Success.
 * @retval SR_ERR_ARG Invalid argument.
 * @retval SR_ERR Other error.
 *
 * @private
 */
SR_PRIV int sr_resource_close(struct sr_context *ctx, struct sr_resource *res)
{
        int ret;

        ret = (*ctx->resource_close_cb)(res, ctx->resource_cb_data);

        if (ret != SR_OK)
                sr_err("Failed to close resource.");

        return ret;
}

/**
 * Read resource data.
 *
 * @param ctx libsigrok context. Must not be NULL.
 * @param[in] res Resource descriptor. Must not be NULL.
 * @param[out] buf Buffer to store @a count bytes into. Must not be NULL.
 * @param count Number of bytes to read.
 *
 * @return The number of bytes actually read, or a negative value on error.
 * @retval SR_ERR_ARG Invalid argument.
 * @retval SR_ERR Other error.
 *
 * @private
 */
SR_PRIV gssize sr_resource_read(struct sr_context *ctx,
                const struct sr_resource *res, void *buf, size_t count)
{
        gssize n_read;

        n_read = (*ctx->resource_read_cb)(res, buf, count,
                        ctx->resource_cb_data);
        if (n_read < 0)
                sr_err("Failed to read resource.");

        return n_read;
}

/**
 * Load a resource into memory.
 *
 * @param ctx libsigrok context. Must not be NULL.
 * @param type Resource type ID.
 * @param name Name of the resource. Must not be NULL.
 * @param[out] size Size in bytes of the returned buffer. Must not be NULL.
 * @param max_size Size limit. Error out if the resource is larger than this.
 *
 * @return A buffer containing the resource data, or NULL on failure. Must
 *  be freed by the caller using g_free().
 *
 * @private
 */
SR_PRIV void *sr_resource_load(struct sr_context *ctx,
                int type, const char *name, size_t *size, size_t max_size)
{
        struct sr_resource res;
        void *buf;
        size_t res_size;
        gssize n_read;

        if (sr_resource_open(ctx, &res, type, name) != SR_OK)
                return NULL;

        if (res.size > max_size) {
                sr_err("Size %" PRIu64 " of '%s' exceeds limit %zu.",
                        res.size, name, max_size);
                sr_resource_close(ctx, &res);
                return NULL;
        }
        res_size = res.size;

        buf = g_try_malloc(res_size);
        if (!buf) {
                sr_err("Failed to allocate buffer for '%s'.", name);
                sr_resource_close(ctx, &res);
                return NULL;
        }

        n_read = sr_resource_read(ctx, &res, buf, res_size);
        sr_resource_close(ctx, &res);

        if (n_read < 0 || (size_t)n_read != res_size) {
                if (n_read >= 0)
                        sr_err("Failed to read '%s': premature end of file.",
                                name);
                g_free(buf);
                return NULL;
        }

        *size = res_size;
        return buf;
}

/** @} */