Port some table-generating stuff from unjpeg.

[fjl] / input.h

diff --git a/input.h b/input.h
index 28c5f0b8530e820101063cef9c0ab83ea6aa0748..34765c25b113b35efff8c77ccf4d3f3e09ae30f0 100644 (file)
--- a/input.h
+++ b/input.h
@@ -21,11 +21,13 @@ static const unsigned bitreservoir_size = 8 * sizeof(bitreservoir_t);
 static const unsigned bitreservoir_fill_size = 8 * sizeof(bitreservoir_fill_t);
 static const unsigned bytereservoir_size = 4096;
 
-// A function to read bytes from some input source.
+// A function to read bytes from some input source. The bytes should be
+// already unstuffed (and thus without markers).
 // A return value of -1 indicates error, a return value of 0 indicates EOF.
 typedef ssize_t (input_func_t)(void*, uint8_t*, size_t);
 
-struct data_source {
+// A data source for efficient reading of bit-level data.
+struct bit_source {
        // Short-term bit reservoir; holds up to 64 bits. When it's empty,
        // it needs to get refilled from the medium-term bit reservoir.
        bitreservoir_t bits;
@@ -41,17 +43,17 @@ struct data_source {
        input_func_t* input_func;
        void* userdata;
 };
-       
-void init_data_source(struct data_source* source, input_func_t* input_func, void* userdata);
+
+void init_bit_source(struct bit_source* source, input_func_t* input_func, void* userdata);
 
 // Internal function. Do not use.
-void possibly_refill_slow_path(struct data_source* source, unsigned num_bits);
+void possibly_refill_slow_path(struct bit_source* source, unsigned num_bits);
 
 // Make sure there's at least NUM_BITS available in the short-term bit reservoir.
 // You usually want to call this before read_bits(). The reason it's separate
 // is that if you want two reads and you know the size of both, it's faster to
 // refill A+B, read A, read B than refill A, read A, refill B, read B.
-static inline void possibly_refill(struct data_source* source, unsigned num_bits)
+static inline void possibly_refill(struct bit_source* source, unsigned num_bits)
 {
        assert(num_bits <= bitreservoir_fill_size + 1);
 
@@ -76,7 +78,7 @@ static inline void possibly_refill(struct data_source* source, unsigned num_bits
        possibly_refill_slow_path(source, num_bits);
 }
 
-static inline unsigned read_bits(struct data_source* source, unsigned num_bits)
+static inline unsigned read_bits(struct bit_source* source, unsigned num_bits)
 {
        assert(source->bits_available >= num_bits);
        unsigned ret = (source->bits >> (bitreservoir_size - num_bits));