#include "io.h"

#include <algorithm>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

struct IOBlock {
	IOBlock *next;
	ssize_t used, size;
	unsigned char data[];
};

IOBlock* newIOBlock() {
	const ssize_t amount = 512*1024; // avoid fragmentation: 128kb is the standard M_MMAP_THRESHOLD
	IOBlock* b = (IOBlock*) malloc(amount);
	if (!b) abort();
	b->size = amount - sizeof(*b);
	b->used = 0;
	b->next = NULL;
	return b;
}

// frees block list
static void blocksToVector(IOBlock *blocks, ssize_t total, std::vector<unsigned char> &buf) {
	buf.reserve(std::max<ssize_t>(total+1, 512*1024)); // try forcing mmap
	buf.resize(total);
	(&buf.at(0))[total] = '\0';
	ssize_t pos = 0;
	IOBlock *prev = 0;
	for (IOBlock *cur = blocks; cur; prev = cur, cur = cur->next) {
		free(prev);
		if (cur->used > 0) {
			memcpy(&buf.at(pos), cur->data, cur->used);
			pos += cur->used;
		}
	}
	free(prev);
}

void readAll(int fd, std::vector<unsigned char> &buf) {
	IOBlock *first = newIOBlock();
	IOBlock *cur = first;
	ssize_t total = 0;
	for (;;) {
		ssize_t avail;
		for (;;) {
			avail = cur->size - cur->used;
			if (0 != avail) break;
			cur->next = newIOBlock();
			cur = cur->next;
		}

		ssize_t len = read(fd, cur->data + cur->used, avail);
		if (0 == len) break; /* eof */
		if (0 > len) {
			perror("read failed");
			abort();
		}
		cur->used += len;
		total += len;
	}
	blocksToVector(first, total, buf);
}

void readLine(int fd, std::vector<unsigned char> &buf) {
	IOBlock *first = newIOBlock();
	IOBlock *cur = first;
	ssize_t total = 0;
	for (;;) {
		if (cur->size == cur->used) {
			cur->next = newIOBlock();
			cur = cur->next;
		}

		ssize_t len = read(fd, cur->data + cur->used, 1);
		if (0 == len) break; /* eof */
		if (0 > len) {
			perror("read failed");
			abort();
		}
		if (cur->data[cur->used] == '\n'  || cur->data[cur->used] == '\r') break;
		cur->used += 1;
		total += 1;
	}
	blocksToVector(first, total, buf);
}