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

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

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

	if(fp->append && fseek(fp, 0, SEEK_END) == EOF) {
		fp->error = 1;
		return 0;
	}

	if(!fp->buf) {
		ssize_t rc = __fp_write(fp, data, size);
		return (rc == EOF) ? 0 : rc;
	}

	__fp_buffer_mode_write(fp);

	size_t size_written = 0;

	while(size_written < size) {
		size_t size_frag = fp->bufsize - fp->bufpos;
		void const *last_line = NULL;

		if(size_frag >= size - size_written) {
			size_frag = size - size_written;

			/* In the last run, if line buffering is enabled and
			   there is a newline, stop at that newline and flush
			   before the last write to buffer */
			if(fp->bufmode == _IOLBF) last_line = memrchr(
				data + size_written, '\n', size_frag);
		}
		if(last_line)
			size_frag = (last_line + 1) - (data + size_written);

		memcpy(fp->buf + fp->bufpos, data + size_written, size_frag);
		size_written += size_frag;
		fp->bufpos += size_frag;

		if(fp->bufpos >= fp->bufsize || last_line) {
			ssize_t rc = __fp_write(fp, fp->buf, fp->bufpos);
			if(rc <= 0) /* error */
				break;
			fp->bufpos = 0;
		}
	}

	return size_written;
}