forked from lix-project/lix
Add a primop for regular expression pattern matching
The function ‘builtins.match’ takes a POSIX extended regular expression and an arbitrary string. It returns ‘null’ if the string does not match the regular expression. Otherwise, it returns a list containing substring matches corresponding to parenthesis groups in the regex. The regex must match the entire string (i.e. there is an implied "^<pat>$" around the regex). For example: match "foo" "foobar" => null match "foo" "foo" => [] match "f(o+)(.*)" "foooobar" => ["oooo" "bar"] match "(.*/)?([^/]*)" "/dir/file.nix" => ["/dir/" "file.nix"] match "(.*/)?([^/]*)" "file.nix" => [null "file.nix"] The following example finds all regular files with extension .nix or .patch underneath the current directory: let findFiles = pat: dir: concatLists (mapAttrsToList (name: type: if type == "directory" then findFiles pat (dir + "/" + name) else if type == "regular" && match pat name != null then [(dir + "/" + name)] else []) (readDir dir)); in findFiles ".*\\.(nix|patch)" (toString ./.)
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@ -1430,7 +1430,34 @@ static void prim_hashString(EvalState & state, const Pos & pos, Value * * args,
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string s = state.forceString(*args[1], context, pos);
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string s = state.forceString(*args[1], context, pos);
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mkString(v, printHash(hashString(ht, s)), context);
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mkString(v, printHash(hashString(ht, s)), context);
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};
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}
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/* Match a regular expression against a string and return either
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‘null’ or a list containing substring matches. */
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static void prim_match(EvalState & state, const Pos & pos, Value * * args, Value & v)
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{
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Regex regex(state.forceStringNoCtx(*args[0], pos), true);
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PathSet context;
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string s = state.forceString(*args[1], context, pos);
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Regex::Subs subs;
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if (!regex.matches(s, subs)) {
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mkNull(v);
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return;
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}
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unsigned int len = subs.empty() ? 0 : subs.rbegin()->first + 1;
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state.mkList(v, len);
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for (unsigned int n = 0; n < len; ++n) {
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auto i = subs.find(n);
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if (i == subs.end())
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mkNull(*(v.list.elems[n] = state.allocValue()));
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else
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mkString(*(v.list.elems[n] = state.allocValue()), i->second);
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}
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}
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/*************************************************************
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/*************************************************************
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@ -1584,6 +1611,7 @@ void EvalState::createBaseEnv()
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addPrimOp("__unsafeDiscardStringContext", 1, prim_unsafeDiscardStringContext);
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addPrimOp("__unsafeDiscardStringContext", 1, prim_unsafeDiscardStringContext);
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addPrimOp("__unsafeDiscardOutputDependency", 1, prim_unsafeDiscardOutputDependency);
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addPrimOp("__unsafeDiscardOutputDependency", 1, prim_unsafeDiscardOutputDependency);
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addPrimOp("__hashString", 2, prim_hashString);
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addPrimOp("__hashString", 2, prim_hashString);
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addPrimOp("__match", 2, prim_match);
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// Versions
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// Versions
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addPrimOp("__parseDrvName", 1, prim_parseDrvName);
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addPrimOp("__parseDrvName", 1, prim_parseDrvName);
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@ -1,13 +1,16 @@
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#include "regex.hh"
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#include "regex.hh"
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#include "types.hh"
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#include "types.hh"
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#include <algorithm>
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namespace nix {
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namespace nix {
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Regex::Regex(const string & pattern)
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Regex::Regex(const string & pattern, bool subs)
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{
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{
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/* Patterns must match the entire string. */
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/* Patterns must match the entire string. */
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int err = regcomp(&preg, ("^(" + pattern + ")$").c_str(), REG_NOSUB | REG_EXTENDED);
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int err = regcomp(&preg, ("^(" + pattern + ")$").c_str(), (subs ? 0 : REG_NOSUB) | REG_EXTENDED);
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if (err) throw Error(format("compiling pattern ‘%1%’: %2%") % pattern % showError(err));
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if (err) throw RegexError(format("compiling pattern ‘%1%’: %2%") % pattern % showError(err));
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nrParens = subs ? std::count(pattern.begin(), pattern.end(), '(') : 0;
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}
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}
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Regex::~Regex()
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Regex::~Regex()
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@ -23,6 +26,20 @@ bool Regex::matches(const string & s)
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throw Error(format("matching string ‘%1%’: %2%") % s % showError(err));
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throw Error(format("matching string ‘%1%’: %2%") % s % showError(err));
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}
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}
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bool Regex::matches(const string & s, Subs & subs)
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{
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regmatch_t pmatch[nrParens + 2];
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int err = regexec(&preg, s.c_str(), nrParens + 2, pmatch, 0);
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if (err == 0) {
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for (unsigned int n = 2; n < nrParens + 2; ++n)
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if (pmatch[n].rm_eo != -1)
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subs[n - 2] = string(s, pmatch[n].rm_so, pmatch[n].rm_eo - pmatch[n].rm_so);
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return true;
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}
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else if (err == REG_NOMATCH) return false;
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throw Error(format("matching string ‘%1%’: %2%") % s % showError(err));
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}
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string Regex::showError(int err)
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string Regex::showError(int err)
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{
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{
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char buf[256];
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char buf[256];
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@ -5,16 +5,23 @@
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#include <sys/types.h>
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#include <sys/types.h>
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#include <regex.h>
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#include <regex.h>
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#include <map>
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namespace nix {
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namespace nix {
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MakeError(RegexError, Error)
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class Regex
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class Regex
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{
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{
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public:
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public:
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Regex(const string & pattern);
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Regex(const string & pattern, bool subs = false);
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~Regex();
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~Regex();
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bool matches(const string & s);
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bool matches(const string & s);
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typedef std::map<unsigned int, string> Subs;
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bool matches(const string & s, Subs & subs);
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private:
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private:
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unsigned nrParens;
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regex_t preg;
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regex_t preg;
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string showError(int err);
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string showError(int err);
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};
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};
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1
tests/lang/eval-okay-regex-match.exp
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1
tests/lang/eval-okay-regex-match.exp
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@ -0,0 +1 @@
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true
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26
tests/lang/eval-okay-regex-match.nix
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26
tests/lang/eval-okay-regex-match.nix
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@ -0,0 +1,26 @@
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with builtins;
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let
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matches = pat: s: match pat s != null;
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splitFN = match "((.*)/)?([^/]*)\\.(nix|cc)";
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in
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assert matches "foobar" "foobar";
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assert matches "fo*" "f";
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assert !matches "fo+" "f";
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assert matches "fo*" "fo";
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assert matches "fo*" "foo";
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assert matches "fo+" "foo";
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assert matches "fo{1,2}" "foo";
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assert !matches "fo{1,2}" "fooo";
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assert !matches "fo*" "foobar";
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assert match "(.*)\\.nix" "foobar.nix" == [ "foobar" ];
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assert splitFN "/path/to/foobar.nix" == [ "/path/to/" "/path/to" "foobar" "nix" ];
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assert splitFN "foobar.cc" == [ null null "foobar" "cc" ];
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true
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