input: Use fseeko/ftello to get the size of a file

[libsigrok.git] / src / input / input.c

diff --git a/src/input/input.c b/src/input/input.c
index fa5a6f7c4f709e72dd6ab52697d35d54a019f148..e93925d2b1c590572d7eb5b66ad7fa839b57d283 100644 (file)
--- a/src/input/input.c
+++ b/src/input/input.c
@@ -19,10 +19,6 @@
 
 #include <config.h>
 #include <string.h>
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <unistd.h>
-#include <fcntl.h>
 #include <errno.h>
 #include <glib.h>
 #include <glib/gstdio.h>
@@ -407,6 +403,43 @@ SR_API int sr_input_scan_buffer(GString *buf, const struct sr_input **in)
        return ret;
 }
 
+/** 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.
+ */
+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;
+}
+
 /**
  * Try to find an input module that can parse the given file.
  *
@@ -416,11 +449,11 @@ SR_API int sr_input_scan_buffer(GString *buf, const struct sr_input **in)
  */
 SR_API int sr_input_scan_file(const char *filename, const struct sr_input **in)
 {
+       int64_t filesize;
        FILE *stream;
        const struct sr_input_module *imod;
        GHashTable *meta;
        GString *header;
-       struct stat st;
        size_t count;
        unsigned int midx, i;
        int ret;
@@ -432,22 +465,18 @@ SR_API int sr_input_scan_file(const char *filename, const struct sr_input **in)
                sr_err("Invalid filename.");
                return SR_ERR_ARG;
        }
-
-       if (!g_file_test(filename, G_FILE_TEST_EXISTS)) {
-               sr_err("No such file.");
-               return SR_ERR_ARG;
-       }
-
-       if (stat(filename, &st) < 0) {
-               sr_err("%s", g_strerror(errno));
-               return SR_ERR_ARG;
-       }
-
        stream = g_fopen(filename, "rb");
        if (!stream) {
                sr_err("Failed to open %s: %s", filename, g_strerror(errno));
                return SR_ERR;
        }
+       filesize = sr_file_get_size(stream);
+       if (filesize < 0) {
+               sr_err("Failed to get size of %s: %s",
+                       filename, g_strerror(errno));
+               fclose(stream);
+               return SR_ERR;
+       }
        /* This actually allocates 256 bytes to allow for NUL termination. */
        header = g_string_sized_new(255);
        count = fread(header->str, 1, header->allocated_len - 1, stream);
@@ -465,7 +494,7 @@ SR_API int sr_input_scan_file(const char *filename, const struct sr_input **in)
        g_hash_table_insert(meta, GINT_TO_POINTER(SR_INPUT_META_FILENAME),
                        (char *)filename);
        g_hash_table_insert(meta, GINT_TO_POINTER(SR_INPUT_META_FILESIZE),
-                       GSIZE_TO_POINTER(st.st_size));
+                       GSIZE_TO_POINTER(MIN(filesize, G_MAXSSIZE)));
        g_hash_table_insert(meta, GINT_TO_POINTER(SR_INPUT_META_HEADER),
                        header);
        midx = 0;