Fixed bug 1913 - state->index may get negative in SDL_wave.c file.
authorSam Lantinga <slouken@libsdl.org>
Tue, 18 Jun 2013 00:50:35 -0700
changeset 7313c7346a060a7d
parent 7312 b36811d7db33
child 7314 b0726d41aa2e
Fixed bug 1913 - state->index may get negative in SDL_wave.c file.

Nitz

In function:
static Sint32
IMA_ADPCM_nibble(struct IMA_ADPCM_decodestate *state, Uint8 nybble)
{
const Sint32 max_audioval = ((1 << (16 - 1)) - 1);
const Sint32 min_audioval = -(1 << (16 - 1));
const int index_table[16] = {
-1, -1, -1, -1,
2, 4, 6, 8,
-1, -1, -1, -1,
2, 4, 6, 8
};
const Sint32 step_table[89] = {
7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 19, 21, 23, 25, 28, 31,
34, 37, 41, 45, 50, 55, 60, 66, 73, 80, 88, 97, 107, 118, 130,
143, 157, 173, 190, 209, 230, 253, 279, 307, 337, 371, 408,
449, 494, 544, 598, 658, 724, 796, 876, 963, 1060, 1166, 1282,
1411, 1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024, 3327,
3660, 4026, 4428, 4871, 5358, 5894, 6484, 7132, 7845, 8630,
9493, 10442, 11487, 12635, 13899, 15289, 16818, 18500, 20350,
22385, 24623, 27086, 29794, 32767
};
Sint32 delta, step;

/* Compute difference and new sample value */
step = step_table[state->index];
// Some Code
}

Here step_table array have the state->index, which might be negative, so it is unsafe to assign this index to step_table array directly.
There would be a check before that to confirm its value.
src/audio/SDL_wave.c
     1.1 --- a/src/audio/SDL_wave.c	Tue Jun 18 00:39:47 2013 -0700
     1.2 +++ b/src/audio/SDL_wave.c	Tue Jun 18 00:50:35 2013 -0700
     1.3 @@ -273,6 +273,11 @@
     1.4      Sint32 delta, step;
     1.5  
     1.6      /* Compute difference and new sample value */
     1.7 +    if (state->index > 88) {
     1.8 +        state->index = 88;
     1.9 +    } else if (state->index < 0) {
    1.10 +        state->index = 0;
    1.11 +    }
    1.12      step = step_table[state->index];
    1.13      delta = step >> 3;
    1.14      if (nybble & 0x04)
    1.15 @@ -287,11 +292,6 @@
    1.16  
    1.17      /* Update index value */
    1.18      state->index += index_table[nybble];
    1.19 -    if (state->index > 88) {
    1.20 -        state->index = 88;
    1.21 -    } else if (state->index < 0) {
    1.22 -        state->index = 0;
    1.23 -    }
    1.24  
    1.25      /* Clamp output sample */
    1.26      if (state->sample > max_audioval) {