New command line parsing infrastructure
This commit is contained in:
Eelco Dolstra
parent
c780c1124e
commit
0db9e6cd1a
6 changed files with 472 additions and 81 deletions
179
src/libutil/args.cc
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179
src/libutil/args.cc
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#include "args.hh"
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#include "hash.hh"
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namespace nix {
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void Args::parseCmdline(const Strings & _cmdline)
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{
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Strings pendingArgs;
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bool dashDash = false;
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Strings cmdline(_cmdline);
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for (auto pos = cmdline.begin(); pos != cmdline.end(); ) {
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auto arg = *pos;
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/* Expand compound dash options (i.e., `-qlf' -> `-q -l -f',
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`-j3` -> `-j 3`). */
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if (!dashDash && arg.length() > 2 && arg[0] == '-' && arg[1] != '-' && isalpha(arg[1])) {
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*pos = (string) "-" + arg[1];
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auto next = pos; ++next;
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for (unsigned int j = 2; j < arg.length(); j++)
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if (isalpha(arg[j]))
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cmdline.insert(next, (string) "-" + arg[j]);
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else {
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cmdline.insert(next, string(arg, j));
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break;
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}
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arg = *pos;
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}
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if (!dashDash && arg == "--") {
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dashDash = true;
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++pos;
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}
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else if (!dashDash && std::string(arg, 0, 1) == "-") {
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if (!processFlag(pos, cmdline.end()))
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throw UsageError(format("unrecognised flag ‘%1%’") % arg);
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}
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else {
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pendingArgs.push_back(*pos++);
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if (processArgs(pendingArgs, false))
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pendingArgs.clear();
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}
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}
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processArgs(pendingArgs, true);
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}
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void Args::printHelp(const string & programName, std::ostream & out)
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{
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std::cout << "Usage: " << programName << " <FLAGS>...";
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for (auto & exp : expectedArgs) {
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std::cout << renderLabels({exp.label});
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// FIXME: handle arity > 1
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if (exp.arity == 0) std::cout << "...";
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}
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std::cout << "\n";
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auto s = description();
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if (s != "")
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std::cout << "\nSummary: " << s << ".\n";
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if (longFlags.size()) {
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std::cout << "\n";
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std::cout << "Flags:\n";
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printFlags(out);
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}
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}
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void Args::printFlags(std::ostream & out)
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{
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Table2 table;
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for (auto & flags : longFlags)
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table.push_back(std::make_pair(
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"--" + flags.first + renderLabels(flags.second.labels),
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flags.second.description));
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printTable(out, table);
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}
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bool Args::processFlag(Strings::iterator & pos, Strings::iterator end)
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{
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assert(pos != end);
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auto process = [&](const std::string & name, const Flag & flag) -> bool {
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++pos;
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Strings args;
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for (size_t n = 0 ; n < flag.arity; ++n) {
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if (pos == end)
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throw UsageError(format("flag ‘%1%’ requires %2% argument(s)")
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% name % flag.arity);
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args.push_back(*pos++);
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}
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flag.handler(args);
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return true;
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};
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if (string(*pos, 0, 2) == "--") {
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auto i = longFlags.find(string(*pos, 2));
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if (i == longFlags.end()) return false;
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return process("--" + i->first, i->second);
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}
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if (string(*pos, 0, 1) == "-" && pos->size() == 2) {
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auto c = (*pos)[1];
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auto i = shortFlags.find(c);
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if (i == shortFlags.end()) return false;
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return process(std::string("-") + c, i->second);
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}
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return false;
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}
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bool Args::processArgs(const Strings & args, bool finish)
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{
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if (expectedArgs.empty()) {
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if (!args.empty())
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throw UsageError(format("unexpected argument ‘%1%’") % args.front());
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return true;
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}
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auto & exp = expectedArgs.front();
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bool res = false;
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if ((exp.arity == 0 && finish) ||
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(exp.arity > 0 && args.size() == exp.arity))
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{
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exp.handler(args);
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expectedArgs.pop_front();
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res = true;
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}
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if (finish && !expectedArgs.empty())
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throw UsageError("more arguments are required");
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return res;
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}
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void Args::mkHashTypeFlag(const std::string & name, HashType * ht)
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{
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mkFlag1(0, name, "TYPE", "hash algorithm (‘md5’, ‘sha1’, ‘sha256’, or ‘sha512’)", [=](std::string s) {
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*ht = parseHashType(s);
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if (*ht == htUnknown)
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throw UsageError(format("unknown hash type ‘%1%’") % s);
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});
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}
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Strings argvToStrings(int argc, char * * argv)
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{
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Strings args;
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argc--; argv++;
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while (argc--) args.push_back(*argv++);
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return args;
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}
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std::string renderLabels(const Strings & labels)
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{
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std::string res;
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for (auto label : labels) {
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for (auto & c : label) c = std::toupper(c);
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res += " <" + label + ">";
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}
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return res;
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}
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void printTable(std::ostream & out, const Table2 & table)
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{
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size_t max = 0;
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for (auto & row : table)
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max = std::max(max, row.first.size());
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for (auto & row : table) {
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out << " " << row.first
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<< std::string(max - row.first.size() + 2, ' ')
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<< row.second << "\n";
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}
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}
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}
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160
src/libutil/args.hh
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160
src/libutil/args.hh
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@ -0,0 +1,160 @@
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#pragma once
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#include <iostream>
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#include <map>
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#include <memory>
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#include "util.hh"
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namespace nix {
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MakeError(UsageError, nix::Error);
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enum HashType : char;
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class Args
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{
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public:
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/* Parse the command line, throwing a UsageError if something goes
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wrong. */
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void parseCmdline(const Strings & cmdline);
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virtual void printHelp(const string & programName, std::ostream & out);
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virtual std::string description() { return ""; }
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protected:
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/* Flags. */
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struct Flag
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{
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std::string description;
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Strings labels;
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size_t arity;
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std::function<void(Strings)> handler;
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};
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std::map<std::string, Flag> longFlags;
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std::map<char, Flag> shortFlags;
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virtual bool processFlag(Strings::iterator & pos, Strings::iterator end);
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void printFlags(std::ostream & out);
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/* Positional arguments. */
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struct ExpectedArg
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{
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std::string label;
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size_t arity; // 0 = any
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std::function<void(Strings)> handler;
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};
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std::list<ExpectedArg> expectedArgs;
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virtual bool processArgs(const Strings & args, bool finish);
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public:
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/* Helper functions for constructing flags / positional
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arguments. */
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void mkFlag(char shortName, const std::string & longName,
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const Strings & labels, const std::string & description,
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size_t arity, std::function<void(Strings)> handler)
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{
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auto flag = Flag{description, labels, arity, handler};
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if (shortName) shortFlags[shortName] = flag;
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longFlags[longName] = flag;
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}
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void mkFlag(char shortName, const std::string & longName,
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const std::string & description, std::function<void()> fun)
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{
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mkFlag(shortName, longName, {}, description, 0, std::bind(fun));
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}
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void mkFlag1(char shortName, const std::string & longName,
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const std::string & label, const std::string & description,
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std::function<void(std::string)> fun)
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{
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mkFlag(shortName, longName, {label}, description, 1, [=](Strings ss) {
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fun(ss.front());
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});
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}
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void mkFlag(char shortName, const std::string & name,
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const std::string & description, bool * dest)
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{
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mkFlag(0, name, description, dest, true);
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}
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void mkFlag(char shortName, const std::string & longName,
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const std::string & label, const std::string & description,
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string * dest)
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{
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mkFlag1(shortName, longName, label, description, [=](std::string s) {
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*dest = s;
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});
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}
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void mkHashTypeFlag(const std::string & name, HashType * ht);
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template<class T>
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void mkFlag(char shortName, const std::string & longName, const std::string & description,
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T * dest, const T & value)
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{
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mkFlag(shortName, longName, {}, description, 0, [=](Strings ss) {
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*dest = value;
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});
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}
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template<class I>
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void mkIntFlag(char shortName, const std::string & longName,
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const std::string & description, I * dest)
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{
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mkFlag<I>(shortName, longName, description, [=](I n) {
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*dest = n;
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});
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}
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template<class I>
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void mkFlag(char shortName, const std::string & longName,
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const std::string & description, std::function<void(I)> fun)
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{
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mkFlag(shortName, longName, {"N"}, description, 1, [=](Strings ss) {
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I n;
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if (!string2Int(ss.front(), n))
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throw UsageError(format("flag ‘--%1%’ requires a integer argument") % longName);
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fun(n);
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});
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}
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/* Expect a string argument. */
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void expectArg(const std::string & label, string * dest)
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{
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expectedArgs.push_back(ExpectedArg{label, 1, [=](Strings ss) {
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*dest = ss.front();
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}});
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}
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/* Expect 0 or more arguments. */
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void expectArgs(const std::string & label, Strings * dest)
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{
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expectedArgs.push_back(ExpectedArg{label, 0, [=](Strings ss) {
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*dest = ss;
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}});
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}
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};
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Strings argvToStrings(int argc, char * * argv);
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/* Helper function for rendering argument labels. */
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std::string renderLabels(const Strings & labels);
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/* Helper function for printing 2-column tables. */
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typedef std::vector<std::pair<std::string, std::string>> Table2;
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void printTable(std::ostream & out, const Table2 & table);
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}
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