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// Copyright 2015 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "extents.h"
#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <stdint.h>
#include <stdlib.h>
#include <algorithm>
#include <limits>
namespace bsdiff {
/* The maximum accepted value for a given integer type when parsed as a signed
* long long integer. This is defined to be the smaller of the maximum value
* that can be represented by this type and LLONG_MAX. This bound allows us to
* properly check that parsed values do not exceed the capacity of their
* intended store, regardless of how its size relates to that of a signed long
* long integer. Note: this may mean that we are losing the most significant
* bit of an unsigned 64-bit field (e.g. size_t on some platforms), however
* still permitting values up to 2^62, which is more than enough for all
* practical purposes. */
#define MAX_ALLOWED(t) \
(std::min(static_cast<uint64_t>(std::numeric_limits<t>::max()), \
static_cast<uint64_t>(std::numeric_limits<long long>::max())))
/* Get the type of a struct field. */
#define FIELD_TYPE(t, f) decltype(((t*)0)->f)
/* Reads a long long integer from |s| into |*val_p|. Returns a pointer to the
* character immediately following the specified |delim|, unless (a) parsing
* failed (overflow or no valid digits); (b) the read value is less than
* |min_val| or greater than |max_val|; (c) the delimiter character is not
* |delim|, or the string ends although |may_end| is false. In any of these
* cases, returns NULL. */
const char* read_llong(const char* s,
long long* val_p,
long long min_val,
long long max_val,
char delim,
int may_end) {
const char* next_s;
errno = 0;
long long val = strtoll(s, (char**)&next_s, 10);
if (((val == LLONG_MAX || val == LLONG_MIN) && errno == ERANGE) ||
next_s == s || val < min_val || val > max_val ||
(*next_s ? *next_s != delim : !may_end))
return NULL; /* bad value or delimiter */
*val_p = val;
if (*next_s)
next_s++; /* skip delimeter */
return next_s;
/* Reads a comma-separated list of "offset:length" extents from |ex_str|. If
* |ex_arr| is NULL, then |ex_count| is ignored and it attempts to parse valid
* extents until the end of the string is reached. Otherwise, stores up to
* |ex_count| extents into |ex_arr|, which must be of at least this size.
* Returns the number of correctly parsed extents, or -1 if a malformed extent
* was found. */
static ssize_t extents_read(const char* ex_str, ex_t* ex_arr, size_t ex_count) {
size_t i;
size_t last_i = ex_count - 1;
if (!ex_arr) {
ex_count = SIZE_MAX;
last_i = 0;
for (i = 0; *ex_str && i < ex_count; i++) {
long long raw_off = 0, raw_len = 0;
if (!((ex_str =
read_llong(ex_str, &raw_off, -1,
MAX_ALLOWED(FIELD_TYPE(ex_t, off)), ':', false)) &&
(ex_str = read_llong(ex_str, &raw_len, 1,
MAX_ALLOWED(FIELD_TYPE(ex_t, len)), ',',
i >= last_i))))
return -1; /* parsing error */
if (ex_arr) {
ex_arr[i].off = raw_off;
ex_arr[i].len = raw_len;
return i;
bool ParseExtentStr(const char* ex_str, std::vector<ex_t>* extents) {
// Sanity check: a string must be provided.
if (!ex_str)
return false;
/* Parse string and count extents. */
ssize_t ret = extents_read(ex_str, NULL, 0);
if (ret < 0)
return false; // parsing error.
// Input is good, commit to extent count.
if (ret == 0)
return true; // No extents, nothing to do.
// Populate the extent array.
extents_read(ex_str, extents->data(), extents->size());
return true;
} // namespace bsdiff