128 lines
3.5 KiB
C
128 lines
3.5 KiB
C
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// infuncmp.c
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// Decodes uncompressed blocks
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#include "inflate.h"
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#include "infmacro.h"
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// Returns whether there are >= n valid bits in the bit buffer
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#define ASSERT_BITS_IN_BIT_BUFFER(n) (context->bitcount + 16 >= (n))
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static int twoBytesToInt(byte a, byte b)
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{
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return (((int) a) & 255) | ((((int) b) & 255) << 8);
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}
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static void dumpBits(t_decoder_context *context, int n)
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{
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context->bitbuf >>= n;
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context->bitcount -= n;
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}
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// retrieve n bits from the bit buffer, and dump them when done
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// n can be up to 16
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static int getBits(t_decoder_context *context, int n)
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{
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int result;
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context->bitcount -= n;
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result = (context->bitbuf & g_BitMask[n]);
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context->bitbuf >>= n;
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return result;
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}
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BOOL decodeUncompressedBlock(t_decoder_context *context, BOOL *end_of_block)
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{
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unsigned int unc_len, complement;
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*end_of_block = FALSE;
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if (context->state == STATE_DECODING_UNCOMPRESSED)
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{
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unc_len = context->state_loop_counter;
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}
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else
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{
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int i;
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if (context->state == STATE_UNCOMPRESSED_ALIGNING)
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{
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// Right now we have between 0 and 32 bits in bitbuf
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// However, we must flush to a byte boundary
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if ((context->bitcount & 7) != 0)
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{
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int result;
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result = getBits(context, (context->bitcount & 7));
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// Since this is supposed to be padding, we should read all zeroes,
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// however, it's not really specified in the spec that they have to
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// be zeroes, so don't count this as an error
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}
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// Now we have exactly 0, 8, 16, 24, or 32 bits in the bit buffer
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context->state = STATE_UNCOMPRESSED_1;
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}
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// Now we need to read 4 bytes from the input - however, some of these bytes may
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// be inside our bit buffer, so take them from there first
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for (i = 0; i < 4; i++)
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{
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if (context->state == STATE_UNCOMPRESSED_1 + i)
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{
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if (ASSERT_BITS_IN_BIT_BUFFER(8))
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{
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context->unc_buffer[i] = (byte) ((context->bitbuf) & 255);
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context->bitbuf >>= 8;
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context->bitcount -= 8;
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}
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else
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{
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if (INPUT_EOF())
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return TRUE;
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context->unc_buffer[i] = *context->input_curpos++;
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}
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context->state++;
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}
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}
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unc_len = twoBytesToInt(context->unc_buffer[0], context->unc_buffer[1]);
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complement = twoBytesToInt(context->unc_buffer[2], context->unc_buffer[3]);
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// make sure complement matches
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if ((unsigned short) unc_len != (unsigned short) (~complement))
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return FALSE; // error!
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}
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// BUGBUG Make this into a memory copy loop for speed!
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while (unc_len > 0 && context->input_curpos < context->end_input_buffer && context->output_curpos < context->end_output_buffer)
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{
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unc_len--;
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*context->output_curpos++ = context->window[context->bufpos++] = *context->input_curpos++;
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context->bufpos &= WINDOW_MASK;
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}
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// More bytes left to compress in this block?
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if (unc_len != 0)
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{
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context->state = STATE_DECODING_UNCOMPRESSED;
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context->state_loop_counter = unc_len;
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}
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else
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{
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// Done with this block, need to re-init bit buffer for next block
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context->state = STATE_READING_BFINAL_NEED_TO_INIT_BITBUF;
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*end_of_block = TRUE;
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}
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return TRUE;
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}
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