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decompress(): Use a Source and Sink

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This allows decompression to happen in O(1) memory.
This commit is contained in:
Eelco Dolstra 2018-03-16 16:59:31 +01:00
parent 64441f0551
commit 3e6b194d78
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GPG key ID: 8170B4726D7198DE
6 changed files with 210 additions and 91 deletions
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75
src/libutil/util.cc
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@ -3,6 +3,7 @@
#include "affinity.hh"
#include "sync.hh"
#include "finally.hh"
#include "serialise.hh"
#include <cctype>
#include <cerrno>
@ -568,19 +569,25 @@ void writeFull(int fd, const string & s, bool allowInterrupts)
string drainFD(int fd)
{
string result;
unsigned char buffer[4096];
StringSink sink;
drainFD(fd, sink);
return std::move(*sink.s);
}
void drainFD(int fd, Sink & sink)
{
std::vector<unsigned char> buf(4096);
while (1) {
checkInterrupt();
ssize_t rd = read(fd, buffer, sizeof buffer);
ssize_t rd = read(fd, buf.data(), buf.size());
if (rd == -1) {
if (errno != EINTR)
throw SysError("reading from file");
}
else if (rd == 0) break;
else result.append((char *) buffer, rd);
else sink(buf.data(), rd);
}
return result;
}
@ -920,20 +927,47 @@ string runProgram(Path program, bool searchPath, const Strings & args,
return res.second;
}
std::pair<int, std::string> runProgram(const RunOptions & options)
std::pair<int, std::string> runProgram(const RunOptions & options_)
{
RunOptions options(options_);
StringSink sink;
options.stdout = &sink;
int status = 0;
try {
runProgram2(options);
} catch (ExecError & e) {
status = e.status;
}
return {status, std::move(*sink.s)};
}
void runProgram2(const RunOptions & options)
{
checkInterrupt();
assert(!(options.stdin && options.input));
std::unique_ptr<Source> source_;
Source * source = options.stdin;
if (options.input) {
source_ = std::make_unique<StringSource>(*options.input);
source = source_.get();
}
/* Create a pipe. */
Pipe out, in;
out.create();
if (options.input) in.create();
if (options.stdout) out.create();
if (source) in.create();
/* Fork. */
Pid pid = startProcess([&]() {
if (dup2(out.writeSide.get(), STDOUT_FILENO) == -1)
if (options.stdout && dup2(out.writeSide.get(), STDOUT_FILENO) == -1)
throw SysError("dupping stdout");
if (options.input && dup2(in.readSide.get(), STDIN_FILENO) == -1)
if (source && dup2(in.readSide.get(), STDIN_FILENO) == -1)
throw SysError("dupping stdin");
Strings args_(options.args);
@ -961,11 +995,20 @@ std::pair<int, std::string> runProgram(const RunOptions & options)
});
if (options.input) {
if (source) {
in.readSide = -1;
writerThread = std::thread([&]() {
try {
writeFull(in.writeSide.get(), *options.input);
std::vector<unsigned char> buf(8 * 1024);
while (true) {
size_t n;
try {
n = source->read(buf.data(), buf.size());
} catch (EndOfFile &) {
break;
}
writeFull(in.writeSide.get(), buf.data(), n);
}
promise.set_value();
} catch (...) {
promise.set_exception(std::current_exception());
@ -974,15 +1017,17 @@ std::pair<int, std::string> runProgram(const RunOptions & options)
});
}
string result = drainFD(out.readSide.get());
if (options.stdout)
drainFD(out.readSide.get(), *options.stdout);
/* Wait for the child to finish. */
int status = pid.wait();
/* Wait for the writer thread to finish. */
if (options.input) promise.get_future().get();
if (source) promise.get_future().get();
return {status, result};
if (status)
throw ExecError(status, fmt("program '%1%' %2%", options.program, statusToString(status)));
}