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FileReader.c
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FileReader.c
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/*
* You may redistribute this program and/or modify it under the terms of
* the GNU General Public License as published by the Free Software Foundation,
* either version 3 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, see <http://www.gnu.org/licenses/>.
*/
#include "io/Reader.h"
#include "io/FileReader.h"
#include "memory/Allocator.h"
#include <string.h>
#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
struct Context {
FILE* toRead;
bool failed;
size_t bytesRead;
struct Reader reader;
};
/** @see Reader->read() */
static int read(void* readInto, size_t length, const struct Reader* reader)
{
struct Context* context = (struct Context*) reader->context;
bool peek = false;
if (length == 0) {
peek = true;
length++;
}
if (context->failed || fread((char*)readInto, 1, length, context->toRead) != length) {
context->failed = true;
return -1;
}
if (peek) {
ungetc(((char*)readInto)[0], context->toRead);
length--;
}
context->bytesRead += length;
return 0;
}
/** @see Reader->bytesRead() */
static size_t bytesRead(const struct Reader* reader)
{
// ftell() is unreliable.
return ((struct Context*) reader->context)->bytesRead;
}
/** @see Reader->skip() */
static void skip(size_t length, const struct Reader* reader)
{
struct Context* context = (struct Context*) reader->context;
#define BUFF_SZ 256
uint8_t buff[BUFF_SZ];
// fseek() and ftell() are unreliable.
size_t amount;
while ((amount = (length > BUFF_SZ) ? BUFF_SZ : length) && !context->failed) {
context->failed = read(buff, amount, reader);
length -= amount;
}
}
/** @see FileReader.h */
struct Reader* FileReader_new(FILE* toRead, const struct Allocator* allocator)
{
struct Context* context = allocator->calloc(sizeof(struct Context), 1, allocator);
context->toRead = toRead;
struct Reader localReader = {
.context = context,
.read = read,
.skip = skip,
.bytesRead = bytesRead
};
memcpy(&context->reader, &localReader, sizeof(struct Reader));
return &context->reader;
}