From ef020c155f6e19c1657241041c4d446debe9923f Mon Sep 17 00:00:00 2001
From: wm4 <wm4@nowhere>
Date: Wed, 24 Jun 2015 14:34:05 +0200
Subject: demux_mkv: allow integer and float elements with length 0

Integer and float elements are encoded as a sequence of bytes prefixed
by a variable-length encoded length specifier. If the length is 0, then
there is no data. Whether this is valid or not is not really clear, but
some sample files which do this have surfaced. It's not particularly
hard to handle this, so just do it.
---
 demux/ebml.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

(limited to 'demux/ebml.c')

diff --git a/demux/ebml.c b/demux/ebml.c
index 91e10213e9..5f1ed37415 100644
--- a/demux/ebml.c
+++ b/demux/ebml.c
@@ -158,7 +158,7 @@ uint64_t ebml_read_uint(stream_t *s)
     uint64_t len, value = 0;
 
     len = ebml_read_length(s);
-    if (len == EBML_UINT_INVALID || len < 1 || len > 8)
+    if (len == EBML_UINT_INVALID || len > 8)
         return EBML_UINT_INVALID;
 
     while (len--)
@@ -177,8 +177,10 @@ int64_t ebml_read_int(stream_t *s)
     int l;
 
     len = ebml_read_length(s);
-    if (len == EBML_UINT_INVALID || len < 1 || len > 8)
+    if (len == EBML_UINT_INVALID || len > 8)
         return EBML_INT_INVALID;
+    if (!len)
+        return 0;
 
     len--;
     l = stream_read_char(s);
@@ -318,7 +320,7 @@ static uint64_t ebml_parse_length(uint8_t *data, size_t data_len, int *length)
 
 static uint64_t ebml_parse_uint(uint8_t *data, int length)
 {
-    assert(length >= 1 && length <= 8);
+    assert(length >= 0 && length <= 8);
     uint64_t r = 0;
     while (length--)
         r = (r << 8) + *data++;
@@ -327,7 +329,9 @@ static uint64_t ebml_parse_uint(uint8_t *data, int length)
 
 static int64_t ebml_parse_sint(uint8_t *data, int length)
 {
-    assert(length >=1 && length <= 8);
+    assert(length >= 0 && length <= 8);
+    if (!length)
+        return 0;
     uint64_t r = 0;
     if (*data & 0x80)
         r = -1;
@@ -338,7 +342,7 @@ static int64_t ebml_parse_sint(uint8_t *data, int length)
 
 static double ebml_parse_float(uint8_t *data, int length)
 {
-    assert(length == 4 || length == 8);
+    assert(length == 0 || length == 4 || length == 8);
     uint64_t i = ebml_parse_uint(data, length);
     if (length == 4)
         return av_int2float(i);
@@ -554,7 +558,7 @@ static void ebml_parse_element(struct ebml_parse_ctx *ctx, void *target,
         case EBML_TYPE_SINT:;
             int64_t *sintptr;
             GETPTR(sintptr, int64_t);
-            if (length < 1 || length > 8) {
+            if (length > 8) {
                 MP_DBG(ctx, "sint invalid length %"PRIu64"\n", length);
                 goto error;
             }
@@ -565,7 +569,7 @@ static void ebml_parse_element(struct ebml_parse_ctx *ctx, void *target,
         case EBML_TYPE_FLOAT:;
             double *floatptr;
             GETPTR(floatptr, double);
-            if (length != 4 && length != 8) {
+            if (length != 0 && length != 4 && length != 8) {
                 MP_DBG(ctx, "float invalid length %"PRIu64"\n", length);
                 goto error;
             }
-- 
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