forked from KolibriOS/kolibrios
95 lines
2.6 KiB
C
95 lines
2.6 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <kolibrisys.h>
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int fread(void *buffer,int size,int count,FILE* file)
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{
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dword res, readbytes;
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dword fullsize, read4cache, toread, readcount;
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if(!file || !buffer)
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{
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errno = E_INVALIDPTR;
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return 0;
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}
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if ((file->mode &3)!=FILE_OPEN_READ && (file->mode & FILE_OPEN_PLUS)==0)
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{
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errno = E_ACCESS;
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return 0;
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}
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fullsize=count*size;
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if (fullsize + file->filepos >= file->filesize)
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{
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fullsize=file->filesize - file->filepos;
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if (fullsize <= 0) return 0;
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}
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/***** file buffering strategy, just read forward *****
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if we read small part - read full buffer, but if buffer have this data - dont read again nothing (or partial read forward 4k pages)
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any writes drops buffers as ungetc_buf */
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read4cache = 0;
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readcount = 0;
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if (file->filepos >= file->buffer_start && file->filepos < file->buffer_end)
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{
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read4cache = min(file->buffer_end - file->filepos, fullsize);
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memcpy(buffer, file->buffer + file->filepos - file->buffer_start, read4cache);
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file->filepos += read4cache;
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if (file->ungetc_buf != EOF) // subst ungetc byte
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{
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*((char*)buffer) = (char)file->ungetc_buf;
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file->ungetc_buf = EOF;
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}
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buffer += read4cache; // ! advance
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fullsize -= read4cache;
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readcount = read4cache / size;
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}
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toread = max(fullsize, file->buffersize);
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if (toread + file->filepos >= file->filesize)
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{
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toread = file->filesize - file->filepos;
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}
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if (fullsize <= 0 || toread <= 0)
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res = 0; // already read or file end
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else
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{
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file->buffer_start = file->filepos;
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if (toread <= fullsize) // read to bigger buffer
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{
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res = _ksys_readfile(file->filename, file->filepos, toread, buffer, &readbytes);
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read4cache = min(readbytes, file->buffersize);
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memcpy(file->buffer, buffer, read4cache);
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file->filepos += readbytes;
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} else
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{
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res = _ksys_readfile(file->filename, file->filepos, toread, file->buffer, &readbytes);
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read4cache = readbytes;
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memcpy(buffer, file->buffer, min(fullsize, read4cache));
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file->filepos += min(fullsize, read4cache);
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}
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file->buffer_end = file->buffer_start + read4cache;
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if (readbytes >= fullsize)
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readcount += fullsize / size;
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else
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readcount += readbytes / size;
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}
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if (file->ungetc_buf != EOF) // subst ungetc byte
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{
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*((char*)buffer) = (char)file->ungetc_buf;
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file->ungetc_buf = EOF;
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}
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if (res != 0)
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{
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file->ungetc_buf = EOF;
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errno = -res;
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}
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return readcount; // really full readed plus cached items
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}
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