X-Git-Url: https://git.sesse.net/?p=fjl;a=blobdiff_plain;f=bitsource.c;h=6cc627c70b08b462b0d0c9c7e0a4ec3d25cdceed;hp=72b143bf7092b666669b3eafb19baf1b7d3bd670;hb=ddc3c24c837f081787825d128675eca628d0e91c;hpb=0b02847989970a190c2cfaec4d1abaa1f616284a

diff --git a/bitsource.c b/bitsource.c
index 72b143b..6cc627c 100644
--- 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;