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// Copyright (C) 2015 the Massachusetts Institute of Technology
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy
// of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
#include "regex__FFI.h"
#include <sys/types.h>
#include <regex.h>
#include <cstring>
extern "C" {
#include <urweb/urweb_cpp.h>
}
#include "config.h"
namespace {
using Regex = uw_Regex__FFI_regex;
using Match = uw_Regex__FFI_match;
// Asserts a condition without crashing or releasing information about where the
// error occurred. This function is essential for web programming, where an
// attacker should not be able to bring down the app by causing an assertion
// failure.
void Assert(uw_context* const context, const bool condition,
const failure_kind action, const char* const message) {
if (!condition) {
uw_error(context, action, message);
}
}
void Assert(uw_context* const context,
const bool condition, const char* const message) {
Assert(context, condition, FATAL, message);
}
void FinalizeRegex(void* regex, [[gnu::unused]] const int _will_retry) {
regfree(reinterpret_cast<regex_t*>(regex));
}
void DeleteRegex(void* regex, [[gnu::unused]] const int _will_retry) {
delete reinterpret_cast<regex_t*>(regex);
}
} // namespace
uw_Basis_bool uw_Regex__FFI_succeeded(
[[gnu::unused]] struct uw_context* _context,
const Match match) {
return match.succeeded ? uw_Basis_True : uw_Basis_False;
}
uw_Basis_int uw_Regex__FFI_n_subexpression_matches(
[[gnu::unused]] struct uw_context* _context,
const Match match) {
return match.n_matches;
}
uw_Basis_string uw_Regex__FFI_subexpression_match(
struct uw_context* context,
const Match match,
const uw_Basis_int match_index) {
Assert(context, match.matches[match_index].rm_so != -1,
"regex: match does not exist");
// Locate the substring in the string to match aginst.
const char* const substring_start =
match.haystack + match.matches[match_index].rm_so;
// Copy it into its own buffer so we can properly null-terminate it.
const std::size_t substring_length =
static_cast<std::size_t>(match.matches[match_index].rm_eo
- match.matches[match_index].rm_so);
uw_Basis_string result = reinterpret_cast<uw_Basis_string>(
uw_malloc(context, substring_length + 1));
std::memcpy(result, substring_start, substring_length);
result[substring_length] = '\0';
return result;
}
Regex uw_Regex__FFI_compile(uw_context* const context,
const uw_Basis_bool case_sensitive,
const uw_Basis_string input) {
Regex result;
result.text = input;
// We'd like to stack-allocate the compiled field of the Regex struct--or, at
// least, to allocate it with uw_malloc. Unfortunately, neither of those will
// work, because we need to be able to run a finalizer on it, and Ur
// finalizers can only reference addresses that are not managed by Ur.
result.compiled = new regex_t;
Assert(context,
uw_register_transactional(context, result.compiled,
nullptr, nullptr, DeleteRegex) == 0,
"regex: could not register DeleteRegex finalizer");
// Compile the regex.
const auto flags = REG_EXTENDED | (case_sensitive ? 0 : REG_ICASE);
switch (const auto regcomp_error = regcomp(result.compiled, input, flags)) {
case 0:
// Everything worked perfectly.
break;
case REG_ESPACE:
// We ran out of memory.
uw_error(context, BOUNDED_RETRY, "regex: could not allocate");
default:
// Something else happened. Generate a nice message for the user.
const auto message_size =
regerror(regcomp_error, result.compiled, nullptr, 0);
char* const message =
reinterpret_cast<char*>(uw_malloc(context, message_size));
Assert(context,
regerror(regcomp_error, result.compiled, message,
message_size) == message_size,
"regex: compilation failed, but error message could not be"
" generated");
uw_error(context, FATAL, "regex: compilation failed: %s", message);
}
Assert(context,
uw_register_transactional(context, result.compiled,
nullptr, nullptr, FinalizeRegex) == 0,
"regex: could not register FinalizeRegex finalizer");
// Give the caller the regex.
return result;
}
Match uw_Regex__FFI_do_match(uw_context* const context, const Regex needle,
const uw_Basis_string haystack) {
Match result;
// Make a duplicate of the string to match against, so if it goes out of scope
// in the calling Ur code, we still have it. TODO(bbaren): Is this necessary?
result.haystack =
reinterpret_cast<uw_Basis_string>(
uw_malloc(context, std::strlen(haystack)));
std::strcpy(result.haystack, haystack);
// Figure out how many groups we could have so we can allocate enough space to
// store the match information.
result.n_matches = 0;
for (std::size_t i = 0; i < std::strlen(needle.text); i++) {
switch (needle.text[i]) {
case '\\':
// The next character is escaped, so it can't possibly be the
// metacharacter '('. Skip it.
i++;
break;
case '(':
// That's our metacharacter.
result.n_matches++;
break;
default:
// Nothing interesting.
break;
}
}
// Allocate to store the match information. Allocate one more slot than we
// need, because the regex engine puts information about the entire match in
// the first slot.
result.matches =
reinterpret_cast<regmatch_t*>(
uw_malloc(context, (result.n_matches + 1) * sizeof(regmatch_t)));
// Execute the regex.
switch (regexec(needle.compiled, haystack, result.n_matches + 1,
result.matches, 0)) {
case 0:
// A match occurred.
result.succeeded = 1;
// Bump the matches array to skip information about the entire match.
result.matches++;
break;
case REG_NOMATCH:
// No match occurred.
result.succeeded = 0;
result.n_matches = 0;
result.matches = nullptr;
break;
case REG_ESPACE:
// We ran out of memory.
uw_error(context, BOUNDED_RETRY, "regex: could not allocate");
default:
// Some unknown error occurred.
uw_error(context, FATAL, "regex: could not execute regular expression");
}
return result;
}
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