lavu/avstring: add av_utf8_decode() function

1 files changed, 64 insertions, 0 deletions

diff --git a/libavutil/avstring.c b/libavutil/avstring.c
index eed58fae1e..20931071b3 100644
--- a/libavutil/avstring.c
+++ b/libavutil/avstring.c
@@ -307,6 +307,70 @@ int av_isxdigit(int c)
     return av_isdigit(c) || (c >= 'a' && c <= 'f');
 }
 
+int av_utf8_decode(int32_t *codep, const uint8_t **bufp, const uint8_t *buf_end,
+                   unsigned int flags)
+{
+    const uint8_t *p = *bufp;
+    uint32_t top;
+    uint64_t code;
+    int ret = 0;
+
+    if (p >= buf_end)
+        return 0;
+
+    code = *p++;
+
+    /* first sequence byte starts with 10, or is 1111-1110 or 1111-1111,
+       which is not admitted */
+    if ((code & 0xc0) == 0x80 || code >= 0xFE) {
+        ret = AVERROR(EILSEQ);
+        goto end;
+    }
+    top = (code & 128) >> 1;
+
+    while (code & top) {
+        int tmp;
+        if (p >= buf_end) {
+            ret = AVERROR(EILSEQ); /* incomplete sequence */
+            goto end;
+        }
+
+        /* we assume the byte to be in the form 10xx-xxxx */
+        tmp = *p++ - 128;   /* strip leading 1 */
+        if (tmp>>6) {
+            ret = AVERROR(EILSEQ);
+            goto end;
+        }
+        code = (code<<6) + tmp;
+        top <<= 5;
+    }
+    code &= (top << 1) - 1;
+
+    if (code >= 1<<31) {
+        ret = AVERROR(EILSEQ);  /* out-of-range value */
+        goto end;
+    }
+
+    *codep = code;
+
+    if (code > 0x10FFFF &&
+        !(flags & AV_UTF8_FLAG_ACCEPT_INVALID_BIG_CODES))
+        ret = AVERROR(EILSEQ);
+    if (code < 0x20 && code != 0x9 && code != 0xA && code != 0xD &&
+        flags & AV_UTF8_FLAG_EXCLUDE_XML_INVALID_CONTROL_CODES)
+        ret = AVERROR(EILSEQ);
+    if (code >= 0xD800 && code <= 0xDFFF &&
+        !(flags & AV_UTF8_FLAG_ACCEPT_SURROGATES))
+        ret = AVERROR(EILSEQ);
+    if (code == 0xFFFE || code == 0xFFFF &&
+        (!flags & AV_UTF8_FLAG_ACCEPT_NON_CHARACTERS))
+        ret = AVERROR(EILSEQ);
+
+end:
+    *bufp = p;
+    return ret;
+}
+
 #ifdef TEST
 
 int main(void)