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-/** @file bits.cc, bit-level output */
-
-/* Copyright (C) 2001, Andrew Stevens <andrew.stevens@philips.com> *
-
- *
- * Disclaimer of Warranty
- *
- * These software programs are available to the user without any license fee or
- * royalty on an "as is" basis. The MPEG Software Simulation Group disclaims
- * any and all warranties, whether express, implied, or statuary, including any
- * implied warranties or merchantability or of fitness for a particular
- * purpose. In no event shall the copyright-holder be liable for any
- * incidental, punitive, or consequential damages of any kind whatsoever
- * arising from the use of these programs.
- *
- * This disclaimer of warranty extends to the user of these programs and user's
- * customers, employees, agents, transferees, successors, and assigns.
- *
- * The MPEG Software Simulation Group does not represent or warrant that the
- * programs furnished hereunder are free of infringement of any third-party
- * patents.
- *
- * Commercial implementations of MPEG-1 and MPEG-2 video, including shareware,
- * are subject to royalty fees to patent holders. Many of these patents are
- * general enough such that they are unavoidable regardless of implementation
- * design.
- *
- */
-
-#include <config.h>
-#include <stdlib.h>
-#include <errno.h>
-#include <string.h>
-#include <sys/param.h>
-#include <assert.h>
-#include "mjpeg_logging.h"
-#include "bits.hh"
-
-
-/// Initializes the bitstream, sets internal variables.
-// TODO: The buffer size should be set dynamically to sensible sizes.
-//
-BitStream::BitStream ():
-user_data (NULL)
-{
- totbits = 0LL;
- buffer_start = 0LL;
- eobs = true;
- readpos = 0LL;
- bfr = 0;
- bfr_size = 0;
-}
-
-/// Deconstructor. Deletes the internal buffer.
-BitStream::~BitStream ()
-{
- delete bfr;
-}
-
-/**
- Refills an IBitStream's input buffer based on the internal variables bufcount and bfr_size.
- */
-bool
-IBitStream::refill_buffer ()
-{
- size_t i;
-
- if (bufcount >= bfr_size) {
- SetBufSize (bfr_size + 4096);
- }
-
- i = read_callback (this, bfr + bufcount, static_cast < size_t > (bfr_size - bufcount), user_data);
- bufcount += i;
-
- if (i == 0) {
- eobs = true;
- return false;
- }
- return true;
-}
-
-/**
- Flushes all read input up-to *but not including* bit
- unbuffer_upto.
-@param flush_to the number of bits to flush
-*/
-
-void
-IBitStream::flush (bitcount_t flush_upto)
-{
- if (flush_upto > buffer_start + bufcount)
- mjpeg_error_exit1 ("INTERNAL ERROR: attempt to flush input beyond buffered amount");
-
- if (flush_upto < buffer_start)
- mjpeg_error_exit1
- ("INTERNAL ERROR: attempt to flush input stream before first buffered byte %d last is %d",
- (int) flush_upto, (int) buffer_start);
- unsigned int bytes_to_flush = static_cast < unsigned int >(flush_upto - buffer_start);
-
- //
- // Don't bother actually flushing until a good fraction of a buffer
- // will be cleared.
- //
-
- if (bytes_to_flush < bfr_size * 3 / 4)
- return;
-
- bufcount -= bytes_to_flush;
- buffer_start = flush_upto;
- byteidx -= bytes_to_flush;
- memmove (bfr, bfr + bytes_to_flush, static_cast < size_t > (bufcount));
-}
-
-
-/**
- Undo scanning / reading
- N.b buffer *must not* be flushed between prepareundo and undochanges.
- @param undo handle to store the undo information
-*/
-void
-IBitStream::prepareundo (BitStreamUndo & undo)
-{
- undo = *(static_cast < BitStreamUndo * >(this));
-}
-
-/**
-Undoes changes committed to an IBitStream.
-@param undo handle to retrieve the undo information
- */
-void
-IBitStream::undochanges (BitStreamUndo & undo)
-{
- *(static_cast < BitStreamUndo * >(this)) = undo;
-}
-
-/**
- Read a number bytes over an IBitStream, using the buffer.
- @param dst buffer to read to
- @param length the number of bytes to read
- */
-unsigned int
-IBitStream::read_buffered_bytes (uint8_t * dst, unsigned int length)
-{
- unsigned int to_read = length;
-
- if (readpos < buffer_start)
- mjpeg_error_exit1
- ("INTERNAL ERROR: access to input stream buffer @ %d: before first buffered byte (%d)",
- (int) readpos, (int) buffer_start);
-
- if (readpos + length > buffer_start + bufcount) {
- /*
- if (!feof (fileh)) {
- mjpeg_error
- ("INTERNAL ERROR: access to input stream buffer beyond last buffered byte @POS=%lld END=%d REQ=%lld + %d bytes",
- readpos, bufcount, readpos - (bitcount_t) buffer_start, length);
- abort ();
- }
- */
- to_read = static_cast < unsigned int >((buffer_start + bufcount) - readpos);
- }
- memcpy (dst, bfr + (static_cast < unsigned int >(readpos - buffer_start)), to_read);
- // We only ever flush up to the start of a read as we
- // have only scanned up to a header *beginning* a block that is then
- // read
- flush (readpos);
- readpos += to_read;
- return to_read;
-}
-
-/** open the device to read the bit stream from it
-@param bs_filename filename to open
-@param buf_size size of the internal buffer
-*/
-void
-IBitStream::open (ReadCallback read_callback, void *user_data, unsigned int buf_size)
-{
- this->read_callback = read_callback;
- this->user_data = user_data;
-
- bfr_size = buf_size;
- if (bfr == NULL)
- bfr = new uint8_t[buf_size];
- else {
- delete bfr;
-
- bfr = new uint8_t[buf_size];
- }
-
- byteidx = 0;
- bitidx = 8;
- totbits = 0LL;
- bufcount = 0;
- eobs = false;
- if (!refill_buffer ()) {
- if (bufcount == 0) {
- mjpeg_error_exit1 ("Unable to read.");
- }
- }
-}
-
-
-/** sets the internal buffer size.
- @param new_buf_size the new internal buffer size
-*/
-void
-IBitStream::SetBufSize (unsigned int new_buf_size)
-{
- assert (bfr != NULL); // Must be open first!
- assert (new_buf_size >= bfr_size); // Can only be increased in size...
-
- if (bfr_size != new_buf_size) {
- uint8_t *new_buf = new uint8_t[new_buf_size];
-
- memcpy (new_buf, bfr, static_cast < size_t > (bfr_size));
- delete bfr;
-
- bfr_size = new_buf_size;
- bfr = new_buf;
- }
-
-}
-
-/**
- close the device containing the bit stream after a read process
-*/
-void
-IBitStream::close ()
-{
-}
-
-
-// TODO replace with shift ops!
-
-uint8_t
- IBitStream::masks[8] = {
- 0x1,
- 0x2,
- 0x4,
- 0x8,
- 0x10,
- 0x20,
- 0x40,
-0x80 };
-
-/*read 1 bit from the bit stream
-@returns the read bit, 0 on EOF */
-uint32_t
-IBitStream::get1bit ()
-{
- unsigned int bit;
-
- if (eobs)
- return 0;
-
- bit = (bfr[byteidx] & masks[bitidx - 1]) >> (bitidx - 1);
- totbits++;
- bitidx--;
- if (!bitidx) {
- bitidx = 8;
- byteidx++;
- if (byteidx == bufcount) {
- refill_buffer ();
- }
- }
-
- return bit;
-}
-
-/*read N bits from the bit stream
-@returns the read bits, 0 on EOF */
-uint32_t
-IBitStream::getbits (int N)
-{
- uint32_t val = 0;
- int i = N;
- unsigned int j;
-
- // Optimize: we are on byte boundary and want to read multiple of bytes!
- if ((bitidx == 8) && ((N & 7) == 0)) {
- i = N >> 3;
- while (i > 0) {
- if (eobs)
- return 0;
- val = (val << 8) | bfr[byteidx];
- byteidx++;
- totbits += 8;
- if (byteidx == bufcount) {
- refill_buffer ();
- }
- i--;
- }
- } else {
- while (i > 0) {
- if (eobs)
- return 0;
-
- j = (bfr[byteidx] & masks[bitidx - 1]) >> (bitidx - 1);
- totbits++;
- bitidx--;
- if (!bitidx) {
- bitidx = 8;
- byteidx++;
- if (byteidx == bufcount) {
- refill_buffer ();
- }
- }
- val = (val << 1) | j;
- i--;
- }
- }
- return val;
-}
-
-
-/** This function seeks for a byte aligned sync word (max 32 bits) in the bit stream and
- places the bit stream pointer right after the sync.
- This function returns 1 if the sync was found otherwise it returns 0
-@param sync the sync word to search for
-@param N the number of bits to retrieve
-@param lim number of bytes to search through
-@returns false on error */
-
-bool
-IBitStream::seek_sync (uint32_t sync, int N, int lim)
-{
- uint32_t val, val1;
- uint32_t maxi = ((1U << N) - 1); /* pow(2.0, (double)N) - 1 */ ;
- if (maxi == 0) {
- maxi = 0xffffffff;
- }
- while (bitidx != 8) {
- get1bit ();
- }
-
- val = getbits (N);
- if (eobs)
- return false;
- while ((val & maxi) != sync && --lim) {
- val <<= 8;
- val1 = getbits (8);
- val |= val1;
- if (eobs)
- return false;
- }
-
- return (!!lim);
-}
-
-
-
-/*
- * Local variables:
- * c-file-style: "stroustrup"
- * tab-width: 4
- * indent-tabs-mode: nil
- * End:
- */
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