1 // Copyright 2015 The Chromium OS Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "extents.h" 6 7 #include <assert.h> 8 #include <errno.h> 9 #include <limits.h> 10 #include <stdint.h> 11 #include <stdlib.h> 12 13 #include <algorithm> 14 #include <limits> 15 16 namespace bsdiff { 17 18 /* The maximum accepted value for a given integer type when parsed as a signed 19 * long long integer. This is defined to be the smaller of the maximum value 20 * that can be represented by this type and LLONG_MAX. This bound allows us to 21 * properly check that parsed values do not exceed the capacity of their 22 * intended store, regardless of how its size relates to that of a signed long 23 * long integer. Note: this may mean that we are losing the most significant 24 * bit of an unsigned 64-bit field (e.g. size_t on some platforms), however 25 * still permitting values up to 2^62, which is more than enough for all 26 * practical purposes. */ 27 #define MAX_ALLOWED(t) \ 28 (std::min(static_cast<uint64_t>(std::numeric_limits<t>::max()), \ 29 static_cast<uint64_t>(std::numeric_limits<long long>::max()))) 30 31 /* Get the type of a struct field. */ 32 #define FIELD_TYPE(t, f) decltype(((t*)0)->f) 33 34 35 /* Reads a long long integer from |s| into |*val_p|. Returns a pointer to the 36 * character immediately following the specified |delim|, unless (a) parsing 37 * failed (overflow or no valid digits); (b) the read value is less than 38 * |min_val| or greater than |max_val|; (c) the delimiter character is not 39 * |delim|, or the string ends although |may_end| is false. In any of these 40 * cases, returns NULL. */ 41 const char* read_llong(const char* s, 42 long long* val_p, 43 long long min_val, 44 long long max_val, 45 char delim, 46 int may_end) { 47 assert(val_p); 48 const char* next_s; 49 errno = 0; 50 long long val = strtoll(s, (char**)&next_s, 10); 51 if (((val == LLONG_MAX || val == LLONG_MIN) && errno == ERANGE) || 52 next_s == s || val < min_val || val > max_val || 53 (*next_s ? *next_s != delim : !may_end)) 54 return NULL; /* bad value or delimiter */ 55 *val_p = val; 56 if (*next_s) 57 next_s++; /* skip delimeter */ 58 return next_s; 59 } 60 61 62 /* Reads a comma-separated list of "offset:length" extents from |ex_str|. If 63 * |ex_arr| is NULL, then |ex_count| is ignored and it attempts to parse valid 64 * extents until the end of the string is reached. Otherwise, stores up to 65 * |ex_count| extents into |ex_arr|, which must be of at least this size. 66 * Returns the number of correctly parsed extents, or -1 if a malformed extent 67 * was found. */ 68 static ssize_t extents_read(const char* ex_str, ex_t* ex_arr, size_t ex_count) { 69 size_t i; 70 size_t last_i = ex_count - 1; 71 if (!ex_arr) { 72 ex_count = SIZE_MAX; 73 last_i = 0; 74 } 75 for (i = 0; *ex_str && i < ex_count; i++) { 76 long long raw_off = 0, raw_len = 0; 77 if (!((ex_str = 78 read_llong(ex_str, &raw_off, -1, 79 MAX_ALLOWED(FIELD_TYPE(ex_t, off)), ':', false)) && 80 (ex_str = read_llong(ex_str, &raw_len, 1, 81 MAX_ALLOWED(FIELD_TYPE(ex_t, len)), ',', 82 i >= last_i)))) 83 return -1; /* parsing error */ 84 if (ex_arr) { 85 ex_arr[i].off = raw_off; 86 ex_arr[i].len = raw_len; 87 } 88 } 89 return i; 90 } 91 92 93 bool ParseExtentStr(const char* ex_str, std::vector<ex_t>* extents) { 94 // Sanity check: a string must be provided. 95 if (!ex_str) 96 return false; 97 98 /* Parse string and count extents. */ 99 ssize_t ret = extents_read(ex_str, NULL, 0); 100 if (ret < 0) 101 return false; // parsing error. 102 103 // Input is good, commit to extent count. 104 extents->resize(ret); 105 if (ret == 0) 106 return true; // No extents, nothing to do. 107 108 // Populate the extent array. 109 extents_read(ex_str, extents->data(), extents->size()); 110 return true; 111 } 112 113 } // namespace bsdiff 114
