#include <stdio.h>
#include <string.h>
#include "fileutil.h"

size_t fread(void *data, size_t membsize, size_t nmemb, FILE *fp)
{
	if(!fp->readable) {
		fp->error = 1;
		return 0;
	}

	size_t request_size;
	if(__builtin_umul_overflow(membsize, nmemb, &request_size)) {
		fp->error = 1;
		return 0;
	}

	/* If the stream if unbuffered, we might have no buffer for the reads.
	   If it's buffered, we always have one. It's also possible that fp is
	   unbuffered (_IONBF) but has a buffer temporarily because ungetc()
	   has been used, in which case we have to transition from buffered
	   reads into direct reads midway. We use __fp_buffered_read() to
	   handle this. */

	size_t read_size = 0;
	__fp_buffer_mode_read(fp);

	while(read_size < request_size) {
		int remaining = request_size - read_size;
		int chunk = __fp_buffered_read(fp, data+read_size, remaining);

		/* Stream is not/no longer buffered, finish unbuffered */
		if(chunk < 0) {
			ssize_t rc = __fp_read(fp, data+read_size, remaining);
			return read_size + (rc == EOF ? 0 : rc);
		}

		read_size += chunk;
		if(read_size >= request_size)
			break;

		/* Get more data from the file descriptor into the buffer */
		if(fp->buf) {
			ssize_t rc = __fp_read(fp, fp->buf, fp->bufsize);
			if(rc <= 0) /* EOF or error */
				break;
			fp->bufread = rc;
		}
	}

	return read_size;
}