Feature: Added functions to parse vorbis comments

src/metadata_xiph.c

@@ -10,8 +10,93 @@
 #include <config.h>
 #endif
 
+#include <stdlib.h>
+#include <string.h>
+
 #include "metadata_xiph.h"
 
 #include "logging.h"
 #define CATMODULE "metadata-xiph"
 
+uint32_t metadata_xiph_read_u32be_unaligned(const unsigned char *in)
+{
+    uint32_t ret = 0;
+    ret += in[3];
+    ret <<= 8;
+    ret += in[2];
+    ret <<= 8;
+    ret += in[1];
+    ret <<= 8;
+    ret += in[0];
+    return ret;
+}
+
+bool     metadata_xiph_read_vorbis_comments(vorbis_comment *vc, const void *buffer, size_t len)
+{
+    bool ret = true;
+    size_t expected_len = 8;
+    uint32_t vendor_len;
+    uint32_t count;
+    uint32_t i;
+    char *out_buffer = NULL;
+    size_t out_buffer_len = 0;
+
+    if (!vc || !buffer || len < expected_len)
+        return false;
+
+    /* reading vendor tag and discarding it */
+    vendor_len = metadata_xiph_read_u32be_unaligned(buffer);
+    expected_len += vendor_len;
+
+    if (len < expected_len)
+        return false;
+
+    buffer += 4 + vendor_len;
+
+    count = metadata_xiph_read_u32be_unaligned(buffer);
+
+    expected_len += count * 4;
+
+    if (len < expected_len)
+        return false;
+
+    buffer += 4;
+
+    for (i = 0; i < count; i++) {
+        uint32_t comment_len = metadata_xiph_read_u32be_unaligned(buffer);
+
+        buffer += 4;
+
+        expected_len += comment_len;
+
+        if (len < expected_len) {
+            ret = false;
+            break;
+        }
+
+        if (out_buffer_len < comment_len || !out_buffer) {
+            char *n_out_buffer = realloc(out_buffer, comment_len + 1);
+            if (!n_out_buffer) {
+                ret = false;
+                break;
+            }
+
+            out_buffer = n_out_buffer;
+            out_buffer_len = comment_len;
+        }
+
+        memcpy(out_buffer, buffer, comment_len);
+        out_buffer[comment_len] = 0;
+        buffer += comment_len;
+
+        vorbis_comment_add(vc, out_buffer);
+    }
+
+    if (!ret) {
+        free(out_buffer);
+        vorbis_comment_clear(vc);
+        vorbis_comment_init(vc);
+    }
+
+    return ret;
+}

src/metadata_xiph.h

@@ -9,4 +9,15 @@
 #ifndef __METADATA_XIPH_H__
 #define __METADATA_XIPH_H__
 
+#include <stdint.h>
+#include <stdbool.h>
+#include <stddef.h> /* for size_t */
+
+#include <vorbis/codec.h>
+
+uint32_t metadata_xiph_read_u32be_unaligned(const unsigned char *in);
+
+/* returns true if parsing was successful, *vc must be in inited state before and will be in inited state after (even when false is returned) */
+bool     metadata_xiph_read_vorbis_comments(vorbis_comment *vc, const void *buffer, size_t len);
+
 #endif