www.gusucode.com > VC++ mp3解压源代码-源码程序 > VC++ mp3解压源代码-源码程序/code/mp3/ibitstr.cpp
//Download by http://www.NewXing.com /* ibitstr.cpp Input bitstream class implementation Changes by Jeff Tsay: 01/26/96 : Modified for Windows file handles. 11/29/96 : Added syncword detection for compatibility with streams produced by DALET. Changed at the request of Wilfried Solbach, thanks for the donation in advance! However Layer I MPP files playback jerkily. 03/09/97 : Added a routine to read layer III side info. Also not mentioned previously are several routines that allow seeking in a stream. 04/14/97 : Moved the side info routine to the layer III decoder object. Revamped the seeking mechanism and also included better syncword detection. Moved the original file reading mechanisms back for better portability, and used John Fehr's implementations of the seeking routines for non-Win32 file reading. */ /* * @(#) ibitstream.cc 1.8, last edit: 6/15/94 16:51:45 * @(#) Copyright (C) 1993, 1994 Tobias Bading (bading@cs.tu-berlin.de) * @(#) Berlin University of Technology * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ /* * Changes from version 1.1 to 1.2: * - third argument in open syscall added * - minor bug in get_header() fixed */ #ifdef __WIN32__ #include <windows.h> #else #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> #include <fcntl.h> #endif // __WIN32__ #ifndef GUI #include <iostream.h> #endif // GUI #include "all.h" #include "ibitstr.h" #include "header.h" #ifdef DAMN_INTEL_BYTE_ORDER #define swap_int32(int_32) (((int_32) << 24) | (((int_32) << 8) & 0x00ff0000) | \ (((int_32) >> 8) & 0x0000ff00) | ((int_32) >> 24)) #endif // DAMN_INTEL_BYTE_ORDER Ibitstream::Ibitstream(const char *filename) { #ifdef __WIN32__ SECURITY_ATTRIBUTES security; security.nLength = sizeof(SECURITY_ATTRIBUTES); security.lpSecurityDescriptor = NULL; security.bInheritHandle = FALSE; fd = CreateFile(filename, GENERIC_READ, FILE_SHARE_READ, &security, OPEN_EXISTING, NULL, NULL); if (fd == INVALID_HANDLE_VALUE) { char bad_file_msg[256]; lstrcpy(bad_file_msg, "Error opening file: "); #ifdef WIN32GUI MessageBox(NULL, lstrcat(bad_file_msg, filename) , "Invalid handle", MB_OK); #else cerr << "Error opening file: " << filename << endl; #endif // WIN32GUI return; } #else // copy any arguments you need, open the file, and check for error if ((fd = open(filename, O_RDONLY)) == -1) { #ifndef GUI cerr << "Error opening file: " << filename << endl; #endif return; } #endif // __WIN32__ wordpointer = buffer; bitindex = 0; // Seeking variables current_frame_number = -1; #ifdef SEEK_STOP last_frame_number = -1; #endif copy = false; } Ibitstream::Ibitstream(const Ibitstream &s0) { int32 i; fd = s0.fd; for (i=0; i<bufferintsize; i++) buffer[i] = s0.buffer[i]; framesize = s0.framesize; wordpointer = buffer + (s0.wordpointer - s0.buffer); bitindex = s0.bitindex; syncword = s0.syncword; single_ch_mode = s0.single_ch_mode; current_frame_number = s0.current_frame_number; #ifdef SEEK_STOP last_frame_number = s0.last_frame_number; #endif copy = true; } // Dummy constructor Ibitstream::Ibitstream() { fd = 0; wordpointer = buffer; bitindex = 0; current_frame_number = -1; #ifdef SEEK_STOP last_frame_number = -1; #endif copy = false; } Ibitstream::~Ibitstream() { // close the file #ifdef __WIN32__ if (fd && !copy) CloseHandle(fd); #else if (fd && !copy) close(fd); #endif } Ibitstream &Ibitstream::operator = (const Ibitstream &s0) { int32 i; fd = s0.fd; for (i=0; i<bufferintsize; i++) buffer[i] = s0.buffer[i]; framesize = s0.framesize; wordpointer = buffer + (s0.wordpointer - s0.buffer); bitindex = s0.bitindex; syncword = s0.syncword; single_ch_mode = s0.single_ch_mode; current_frame_number = s0.current_frame_number; #ifdef SEEK_STOP last_frame_number = s0.last_frame_number; #endif copy = true; return *this; } bool Ibitstream::get_header (uint32 *headerstring, enum e_syncmode syncmode) { bool result, sync; int32 numread; do { // Read 4 bytes from the file, placing the number of bytes actually // read in numread #ifdef __WIN32__ result = (bool) ReadFile(fd, (char *) headerstring, 4, (DWORD *) &numread, NULL); #else if (fd == -1) return false; // check for error opening file result = (bool) ((numread=read(fd, (char*) headerstring, 4)) == 4); #endif if (!(result && (numread == 4))) return false; #ifdef DAMN_INTEL_BYTE_ORDER if (syncmode == INITIAL_SYNC) { sync = ((*headerstring & 0x0000F0FF) == 0x0000F0FF); } else { sync = ((*headerstring & 0x000CF8FF) == syncword) && (((*headerstring & 0xC0000000) == 0xC0000000) == single_ch_mode); } #else if (syncmode == INITIAL_SYNC) { sync = ((*headerstring & 0xFFF00000) == 0xFFF00000); } else { sync = ((*headerstring & 0xFFF80C00) == syncword) && (((*headerstring & 0x000000C0) == 0x000000C0) == single_ch_mode); } #endif // DAMN_INTEL_BYTE_ORDER if (!sync) // rewind 3 bytes in the file so we can try to sync again, if // successful set result to true #ifdef __WIN32__ result = (bool) SetFilePointer(fd, -3, NULL, FILE_CURRENT); #else result = (bool) (lseek(fd, -3, SEEK_CUR) != -1); #endif // __WIN32__ } while (!sync && result); if (!result) return false; #ifdef DAMN_INTEL_BYTE_ORDER uint32 header = *headerstring; *headerstring = swap_int32(header); #endif // DAMN_INTEL_BYTE_ORDER current_frame_number++; #ifdef SEEK_STOP if (last_frame_number < current_frame_number) last_frame_number = current_frame_number; #endif return true; } bool Ibitstream::read_frame(uint32 bytesize) { int32 numread; // read bytesize bytes from the file, placing the number of bytes // actually read in numread and setting result to true if // successful #ifdef __WIN32__ bool result = ReadFile(fd, buffer, bytesize, (DWORD *) &numread, NULL); #else bool result = (bool) ((numread=read(fd,buffer,bytesize)) != -1); #endif // __WIN32__ /* if (bytesize > (bufferintsize << 2)) { cerr << "Internal error: framelength > bufferlength?!\n"; exit (1); } */ wordpointer = buffer; bitindex = 0; framesize = bytesize; #ifdef DAMN_INTEL_BYTE_ORDER uint32 *wordp; for (wordp = buffer + ((bytesize - 1) >> 2); wordp >= buffer; --wordp) { #ifdef INTEL386 // inline 386 assembly doesn't work on Borland compiler __asm { mov eax, wordp mov ebx, [eax] bswap ebx mov [eax], ebx } #else uint32 word = *wordp; *wordp = swap_int32(word); #endif // INTEL386 } // for (wordp ... #endif // DAMN_INTEL_BYTE_ORDER return((bool) (result && (numread == framesize))); } uint32 Ibitstream::get_bits(uint32 number_of_bits) { static uint32 bitmask[18] = { 0, // dummy 0x00000001, 0x00000003, 0x00000007, 0x0000000F, 0x0000001F, 0x0000003F, 0x0000007F, 0x000000FF, 0x000001FF, 0x000003FF, 0x000007FF, 0x00000FFF, 0x00001FFF, 0x00003FFF, 0x00007FFF, 0x0000FFFF, 0x0001FFFF }; uint32 returnvalue; uint32 sum = bitindex + number_of_bits; if (sum <= 32) { // all bits contained in *wordpointer returnvalue = (*wordpointer >> (32 - sum)) & bitmask[number_of_bits]; if ((bitindex += number_of_bits) == 32) { bitindex = 0; /* if ((char *)++wordpointer > (char *)buffer + framesize) { cerr << "Ibitstream::get_bits(): no more bits in buffer!\n"; exit (1); } */ wordpointer++; // added by me! } return returnvalue; } #ifdef DAMN_INTEL_BYTE_ORDER *((int16 *)&returnvalue + 1) = *(int16 *)wordpointer; wordpointer++; // Added by me! *(int16 *)&returnvalue = *((int16 *)wordpointer + 1); #else *(int16 *)&returnvalue = *((int16 *)wordpointer + 1); wordpointer++; // Added by me! *((int16 *)&returnvalue + 1) = *(int16 *)wordpointer; #endif // DAMN_INTEL_BYTE_ORDER returnvalue >>= 48 - sum; // returnvalue >>= 16 - (number_of_bits - (32 - bitindex)) returnvalue &= bitmask[number_of_bits]; bitindex = sum - 32; return returnvalue; } void Ibitstream::set_syncword(uint32 syncword0) { #ifdef DAMN_INTEL_BYTE_ORDER syncword = swap_int32(syncword0 & 0xFFFFFF3F); #else syncword = syncword0 & 0xFFFFFF3F; #endif // DAMN_INTEL_BYTE_ORDER single_ch_mode = ((syncword0 & 0x000000C0) == 0x000000C0); } uint32 Ibitstream::file_size() const // return the file size of the file { #ifdef __WIN32__ return GetFileSize(fd, NULL); #else // hmm. I think this should work -- John Fehr off_t o_off; off_t len; o_off = lseek(fd, 0, SEEK_CUR); len = lseek(fd, 0, SEEK_END); lseek(fd, o_off, SEEK_SET); return len; #endif // __WIN32__ } #ifdef SEEK_STOP bool Ibitstream::seek(int32 frame, int32 frame_size) // set the file pointer to frame * (frame_size + 4) bytes after the // beginning of the file and return true if successful { current_frame_number = frame - 1; #ifdef __WIN32__ return(SetFilePointer(fd, frame * (frame_size + 4), NULL, FILE_BEGIN) != 0xFFFFFFFF); #else return lseek(fd, frame * (frame_size + 4), SEEK_SET); #endif // __WIN32__ } bool Ibitstream::seek_pad(int32 frame, int32 base_frame_size, Header *header, uint32 *offset) { // base_frame_size is the frame size _without_ padding. Crc16 *crc = NULL; int32 total_frame_size = base_frame_size + 4; int32 diff; if (last_frame_number < frame) { diff = (last_frame_number >= 0) ? offset[last_frame_number] : 0; // set the file pointer to ((last_frame_number+1) * total_frame_size) // bytes after the beginning of the file #ifdef __WIN32__ SetFilePointer(fd, (last_frame_number + 1) * total_frame_size + diff, NULL, FILE_BEGIN); #else lseek(fd, (last_frame_number + 1) * total_frame_size + diff, SEEK_SET); #endif // __WIN32__ current_frame_number = last_frame_number; do { if (!header->read_header(this, &crc)) // will increment last_frame_number return false; } while (last_frame_number < frame); return true; } else { diff = (frame > 0) ? offset[frame - 1] : 0; // set the file pointer to (frame * total_frame_size + diff) bytes // after the beginning of the file #ifdef __WIN32__ SetFilePointer(fd, frame * total_frame_size + diff, NULL, FILE_BEGIN); #else lseek(fd, frame * total_frame_size + diff, SEEK_SET); #endif // __WIN32__ current_frame_number = frame - 1; return header->read_header(this, &crc); } } #endif // SEEK_STOP