140 lines
4 KiB
C
140 lines
4 KiB
C
/*
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** buffers.c - Routines dealing with I/O and expansion buffers for LZCopy()
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** and DOS command-line programs.
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**
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** Author: DavidDi
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*/
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// Headers
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///////////
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#ifndef LZA_DLL
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#include <dos.h>
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#include <fcntl.h>
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#endif
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#include "lz_common.h"
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#include "lz_buffers.h"
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/*
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** int ReadInBuf(BYTE ARG_PTR *pbyte, int doshSource);
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**
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** Read input file into input buffer.
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**
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** Arguments: pbyte - pointer to storage for first byte read from file
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** into buffer
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** doshSource - DOS file handle to open input file
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**
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** Returns: int - TRUE or END_OF_INPUT if successful. LZERROR_BADINHANDLE
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** if not.
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**
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** Globals: rgbyteInBuf[0] - holds last byte from previous buffer
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** pbyteInBufEnd - set to point to first byte beyond end of data
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** in input buffer
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** bLastUsed - reset to FALSE if currently TRUE
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*/
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INT ReadInBuf(BYTE ARG_PTR *pbyte, INT doshSource, PLZINFO pLZI)
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{
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DWORD ucbRead; // number of bytes actually read
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// !!! Assumes pLZI parm is valid. No sanity check (should be done above in caller).
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pLZI->rgbyteInBuf[0] = *(pLZI->pbyteInBufEnd - 1);
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if ((ucbRead = FREAD(doshSource, &pLZI->rgbyteInBuf[1], pLZI->ucbInBufLen))
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!= pLZI->ucbInBufLen)
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{
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#ifdef LZA_DLL
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if (ucbRead == (DWORD)(-1)) {
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#else
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if (_error != 0U) {
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#endif
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// We were handed a bad input file handle.
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return(LZERROR_BADINHANDLE);
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}
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else if (ucbRead > 0U)
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// Read last ucbRead bytes of input file. Change input buffer end
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// to account for shorter read.
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pLZI->pbyteInBufEnd = &pLZI->rgbyteInBuf[1] + ucbRead;
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else { // (ucbRead == 0U) {
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// We couldn't read any bytes from input file (EOF reached).
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return(END_OF_INPUT);
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}
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}
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// Reset read pointer to beginning of input buffer.
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pLZI->pbyteInBuf = &pLZI->rgbyteInBuf[1];
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// Was an UnreadByte() done at the beginning of the last buffer?
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if (pLZI->bLastUsed)
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{
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// Return the last byte from the previous input buffer
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*pbyte = pLZI->rgbyteInBuf[0];
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pLZI->bLastUsed = FALSE;
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}
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else
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// Return the first byte from the new input buffer.
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*pbyte = *pLZI->pbyteInBuf++;
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return(TRUE);
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}
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/*
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** int WriteOutBuf(BYTE byteNext, int doshDest);
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**
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** Dumps output buffer to output file. Prompts for new floppy disk if the
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** old one if full. Continues dumping to output file of same name on new
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** floppy disk.
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**
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** Arguments: byteNext - first byte to be added to empty buffer after buffer
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** is written
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** doshDest - output DOS file handle
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**
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** Returns: int - TRUE if successful. LZERROR_BADOUTHANDLE or
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** LZERROR_WRITE if unsuccessful.
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**
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** Globals: pbyteOutBuf - reset to point to free byte after byteNext in
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** rgbyteOutBuf
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*/
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INT WriteOutBuf(BYTE byteNext, INT doshDest, PLZINFO pLZI)
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{
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DWORD ucbToWrite, // number of bytes to write from buffer
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ucbWritten, // number of bytes actually written
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ucbTotWritten; // total number of bytes written to output
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// !!! Assumes pLZI parm is valid. No sanity check (should be done above in caller).
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// How much of the buffer should be written to the output file?
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ucbTotWritten = ucbToWrite = (DWORD)(pLZI->pbyteOutBuf - pLZI->rgbyteOutBuf);
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// Reset pointer to beginning of buffer.
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pLZI->pbyteOutBuf = pLZI->rgbyteOutBuf;
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// Write to ouput file.
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if (doshDest != NO_DOSH &&
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(ucbWritten = FWRITE(doshDest, pLZI->pbyteOutBuf, ucbToWrite)) != ucbToWrite)
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{
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#ifdef LZA_DLL
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if (ucbWritten == (DWORD)(-1)) {
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#else
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if (_error != 0U) {
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#endif
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// Bad DOS file handle.
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return(LZERROR_BADOUTHANDLE);
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}
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else {
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// Insufficient space on destination drive.
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return(LZERROR_WRITE);
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}
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}
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// Add the next byte to the buffer.
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*pLZI->pbyteOutBuf++ = byteNext;
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return(TRUE);
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}
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