The bit source needs to actually consume the data it passes by...

[fjl] / bitsource.c

diff --git a/bitsource.c b/bitsource.c
index 72b143bf7092b666669b3eafb19baf1b7d3bd670..6cc627c70b08b462b0d0c9c7e0a4ec3d25cdceed 100644 (file)
--- a/bitsource.c
+++ b/bitsource.c
@@ -12,15 +12,20 @@ void init_bit_source(struct bit_source* source, input_func_t* input_func, void*
 {
        memset(source, 0, sizeof(*source));
        source->bytes = (uint8_t*)malloc(BYTERESERVOIR_SIZE);
+       source->byte_read_ptr = source->bytes;
        source->input_func = input_func;
        source->userdata = userdata;
 }
 
 void possibly_refill_slow_path(struct bit_source* source, unsigned num_bits)
 {
-       // First, make sure there's stuff in the byte reservoir if we can.
+       // First, move out the data we already read.
        assert(source->bytes_available <= BYTERESERVOIR_SIZE);
+       assert(source->byte_read_ptr >= source->bytes);
+       memmove(source->bytes, source->byte_read_ptr, source->bytes_available);
+       source->byte_read_ptr = source->bytes;
 
+       // Then, make sure there's stuff in the byte reservoir if we can.
        // Read data from the source until we have enough to satisfy the request.
        while (source->bits_available + 8 * source->bytes_available < num_bits) {
                const size_t bytes_to_read = BYTERESERVOIR_SIZE - source->bytes_available;
@@ -50,8 +55,8 @@ void possibly_refill_slow_path(struct bit_source* source, unsigned num_bits)
        while (source->bits_available < num_bits) {
                assert(source->bytes_available > 0);
                assert(source->bits_available + 8 <= BITRESERVOIR_SIZE);
-               uint8_t byte = *(source->bytes);
-               ++source->bytes;
+               uint8_t byte = *(source->byte_read_ptr);
+               ++source->byte_read_ptr;
                --source->bytes_available;
                source->bits |= ((bitreservoir_t)byte << (BITRESERVOIR_SIZE - source->bits_available - 8));
                source->bits_available += 8;