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#pragma once
///@file
#include <memory>
#include "charptr-cast.hh"
#include "generator.hh"
#include "types.hh"
#include "file-descriptor.hh"
namespace nix {
/**
* Abstract destination of binary data.
*/
struct Sink
{
virtual ~Sink() { }
virtual void operator () (std::string_view data) = 0;
virtual bool good() { return true; }
};
/**
* Just throws away data.
*/
struct NullSink : Sink
{
void operator () (std::string_view data) override
{ }
};
struct FinishSink : virtual Sink
{
virtual void finish() = 0;
};
/**
* A buffered abstract sink. Warning: a BufferedSink should not be
* used from multiple threads concurrently.
*/
struct BufferedSink : virtual Sink
{
size_t bufSize, bufPos;
std::unique_ptr<char[]> buffer;
BufferedSink(size_t bufSize = 32 * 1024)
: bufSize(bufSize), bufPos(0), buffer(nullptr) { }
void operator () (std::string_view data) override;
void flush();
protected:
virtual void writeUnbuffered(std::string_view data) = 0;
};
/**
* Abstract source of binary data.
*/
struct Source
{
virtual ~Source() { }
/**
* Store exactly ‘len’ bytes in the buffer pointed to by ‘data’.
* It blocks until all the requested data is available, or throws
* an error if it is not going to be available.
*/
void operator () (char * data, size_t len);
/**
* Store up to ‘len’ in the buffer pointed to by ‘data’, and
* return the number of bytes stored. It blocks until at least
* one byte is available.
*
* Should not return 0 (generally you want to throw EndOfFile), but nothing
* stops that.
*
* \throws EndOfFile if there is no more data.
*/
virtual size_t read(char * data, size_t len) = 0;
virtual bool good() { return true; }
void drainInto(Sink & sink);
std::string drain();
};
/**
* A buffered abstract source. Warning: a BufferedSource should not be
* used from multiple threads concurrently.
*/
struct BufferedSource : Source
{
size_t bufSize, bufPosIn, bufPosOut;
std::unique_ptr<char[]> buffer;
BufferedSource(size_t bufSize = 32 * 1024)
: bufSize(bufSize), bufPosIn(0), bufPosOut(0), buffer(nullptr) { }
size_t read(char * data, size_t len) override;
bool hasData();
protected:
/**
* Underlying read call, to be overridden.
*/
virtual size_t readUnbuffered(char * data, size_t len) = 0;
};
/**
* A sink that writes data to a file descriptor.
*/
struct FdSink : BufferedSink
{
int fd;
size_t written = 0;
FdSink() : fd(-1) { }
FdSink(int fd) : fd(fd) { }
FdSink(FdSink&&) = default;
FdSink & operator=(FdSink && s)
{
flush();
fd = s.fd;
s.fd = -1;
written = s.written;
return *this;
}
~FdSink();
void writeUnbuffered(std::string_view data) override;
bool good() override;
private:
bool _good = true;
};
/**
* A source that reads data from a file descriptor.
*/
struct FdSource : BufferedSource
{
int fd;
size_t read = 0;
/** Defaults to "unexpected end-of-file" */
std::optional<std::string> specialEndOfFileError;
std::string endOfFileError() const;
FdSource() : fd(-1) { }
FdSource(int fd) : fd(fd) { }
FdSource(FdSource &&) = default;
FdSource & operator=(FdSource && s)
{
fd = s.fd;
s.fd = -1;
read = s.read;
return *this;
}
bool good() override;
protected:
size_t readUnbuffered(char * data, size_t len) override;
private:
bool _good = true;
};
/**
* A sink that writes data to a string.
*/
struct StringSink : Sink
{
std::string s;
StringSink() { }
explicit StringSink(const size_t reservedSize)
{
s.reserve(reservedSize);
};
StringSink(std::string && s) : s(std::move(s)) { };
void operator () (std::string_view data) override;
};
/**
* A source that reads data from a string.
*/
struct StringSource : Source
{
std::string_view s;
size_t pos;
StringSource(std::string_view s) : s(s), pos(0) { }
size_t read(char * data, size_t len) override;
};
/**
* A sink that writes all incoming data to two other sinks.
*/
struct TeeSink : Sink
{
Sink & sink1, & sink2;
TeeSink(Sink & sink1, Sink & sink2) : sink1(sink1), sink2(sink2) { }
virtual void operator () (std::string_view data) override
{
sink1(data);
sink2(data);
}
};
/**
* Adapter class of a Source that saves all data read to a sink.
*/
struct TeeSource : Source
{
Source & orig;
Sink & sink;
TeeSource(Source & orig, Sink & sink)
: orig(orig), sink(sink) { }
size_t read(char * data, size_t len) override
{
size_t n = orig.read(data, len);
sink({data, n});
return n;
}
};
/**
* A reader that consumes the original Source until 'size'.
*/
struct SizedSource : Source
{
Source & orig;
size_t remain;
SizedSource(Source & orig, size_t size)
: orig(orig), remain(size) { }
size_t read(char * data, size_t len) override
{
if (this->remain <= 0) {
throw EndOfFile("sized: unexpected end-of-file");
}
len = std::min(len, this->remain);
size_t n = this->orig.read(data, len);
this->remain -= n;
return n;
}
/**
* Consume the original source until no remain data is left to consume.
*/
size_t drainAll()
{
std::vector<char> buf(8192);
size_t sum = 0;
while (this->remain > 0) {
size_t n = read(buf.data(), buf.size());
sum += n;
}
return sum;
}
};
/**
* A sink that that just counts the number of bytes given to it
*/
struct LengthSink : Sink
{
uint64_t length = 0;
void operator () (std::string_view data) override
{
length += data.size();
}
};
/**
* Convert a function into a sink.
*/
struct LambdaSink : Sink
{
typedef std::function<void(std::string_view data)> lambda_t;
lambda_t lambda;
LambdaSink(const lambda_t & lambda) : lambda(lambda) { }
void operator () (std::string_view data) override
{
lambda(data);
}
};
/**
* Convert a function into a source.
*/
struct LambdaSource : Source
{
typedef std::function<size_t(char *, size_t)> lambda_t;
lambda_t lambda;
LambdaSource(const lambda_t & lambda) : lambda(lambda) { }
size_t read(char * data, size_t len) override
{
return lambda(data, len);
}
};
/**
* Chain two sources together so after the first is exhausted, the second is
* used
*/
struct ChainSource : Source
{
Source & source1, & source2;
bool useSecond = false;
ChainSource(Source & s1, Source & s2)
: source1(s1), source2(s2)
{ }
size_t read(char * data, size_t len) override;
};
struct GeneratorSource : Source
{
GeneratorSource(Generator<Bytes> && g) : g(std::move(g)) {}
virtual size_t read(char * data, size_t len) override
{
// we explicitly do not poll the generator multiple times to fill the
// buffer, only to produce some output at all. this is allowed by the
// semantics of read(), only operator() must fill the buffer entirely
while (!buf.size()) {
if (auto next = g.next()) {
buf = *next;
} else {
throw EndOfFile("coroutine has finished");
}
}
len = std::min(len, buf.size());
memcpy(data, buf.data(), len);
buf = buf.subspan(len);
return len;
}
private:
Generator<Bytes> g;
Bytes buf{};
};
inline Sink & operator<<(Sink & sink, Generator<Bytes> && g)
{
while (auto buffer = g.next()) {
sink(std::string_view(buffer->data(), buffer->size()));
}
return sink;
}
struct SerializingTransform;
using WireFormatGenerator = Generator<Bytes, SerializingTransform>;
struct SerializingTransform
{
std::array<unsigned char, 8> buf;
Bytes operator()(uint64_t n)
{
buf[0] = n & 0xff;
buf[1] = (n >> 8) & 0xff;
buf[2] = (n >> 16) & 0xff;
buf[3] = (n >> 24) & 0xff;
buf[4] = (n >> 32) & 0xff;
buf[5] = (n >> 40) & 0xff;
buf[6] = (n >> 48) & 0xff;
buf[7] = (unsigned char) (n >> 56) & 0xff;
return {charptr_cast<const char *>(buf.begin()), 8};
}
static Bytes padding(size_t unpadded)
{
return Bytes("\0\0\0\0\0\0\0", unpadded % 8 ? 8 - unpadded % 8 : 0);
}
// opt in to generator chaining. without this co_yielding
// another generator of any type will cause a type error.
auto operator()(Generator<Bytes> && g)
{
return std::move(g);
}
// only choose this for *exactly* char spans, do not allow implicit
// conversions. this would cause ambiguities with strings literals,
// and resolving those with more string-like overloads needs a lot.
template<typename Span>
requires std::same_as<Span, std::span<char>> || std::same_as<Span, std::span<const char>>
Bytes operator()(Span s)
{
return s;
}
WireFormatGenerator operator()(std::string_view s);
WireFormatGenerator operator()(const Strings & s);
WireFormatGenerator operator()(const StringSet & s);
WireFormatGenerator operator()(const Error & s);
};
void writePadding(size_t len, Sink & sink);
// NOLINTBEGIN(cppcoreguidelines-avoid-capturing-lambda-coroutines):
// These coroutines do their entire job before the semicolon and are not
// retained, so they live long enough.
inline Sink & operator<<(Sink & sink, uint64_t u)
{
return sink << [&]() -> WireFormatGenerator { co_yield u; }();
}
inline Sink & operator<<(Sink & sink, std::string_view s)
{
return sink << [&]() -> WireFormatGenerator { co_yield s; }();
}
inline Sink & operator<<(Sink & sink, const Strings & s)
{
return sink << [&]() -> WireFormatGenerator { co_yield s; }();
}
inline Sink & operator<<(Sink & sink, const StringSet & s)
{
return sink << [&]() -> WireFormatGenerator { co_yield s; }();
}
inline Sink & operator<<(Sink & sink, const Error & ex)
{
return sink << [&]() -> WireFormatGenerator { co_yield ex; }();
}
// NOLINTEND(cppcoreguidelines-avoid-capturing-lambda-coroutines)
MakeError(SerialisationError, Error);
template<typename T>
T readNum(Source & source);
inline unsigned int readInt(Source & source)
{
return readNum<unsigned int>(source);
}
inline uint64_t readLongLong(Source & source)
{
return readNum<uint64_t>(source);
}
void readPadding(size_t len, Source & source);
size_t readString(char * buf, size_t max, Source & source);
std::string readString(Source & source, size_t max = std::numeric_limits<size_t>::max());
template<class T> T readStrings(Source & source);
Source & operator >> (Source & in, std::string & s);
template<typename T>
Source & operator >> (Source & in, T & n)
{
n = readNum<T>(in);
return in;
}
template<typename T>
Source & operator >> (Source & in, bool & b)
{
b = readNum<uint64_t>(in);
return in;
}
Error readError(Source & source);
/**
* An adapter that converts a std::basic_istream into a source.
*/
struct StreamToSourceAdapter : Source
{
std::shared_ptr<std::basic_istream<char>> istream;
StreamToSourceAdapter(std::shared_ptr<std::basic_istream<char>> istream)
: istream(istream)
{ }
size_t read(char * data, size_t len) override
{
if (!istream->read(data, len)) {
if (istream->eof()) {
if (istream->gcount() == 0)
throw EndOfFile("end of file");
} else
throw Error("I/O error in StreamToSourceAdapter");
}
return istream->gcount();
}
};
/**
* A source that reads a distinct format of concatenated chunks back into its
* logical form, in order to guarantee a known state to the original stream,
* even in the event of errors.
*
* Use with FramedSink, which also allows the logical stream to be terminated
* in the event of an exception.
*/
struct FramedSource : Source
{
Source & from;
bool eof = false;
std::vector<char> pending;
size_t pos = 0;
FramedSource(Source & from) : from(from)
{ }
~FramedSource()
{
try {
if (!eof) {
while (true) {
auto n = readInt(from);
if (!n) break;
std::vector<char> data(n);
from(data.data(), n);
}
}
} catch (...) {
ignoreExceptionInDestructor();
}
}
size_t read(char * data, size_t len) override
{
if (eof) throw EndOfFile("reached end of FramedSource");
if (pos >= pending.size()) {
size_t len = readInt(from);
if (!len) {
eof = true;
return 0;
}
pending = std::vector<char>(len);
pos = 0;
from(pending.data(), len);
}
auto n = std::min(len, pending.size() - pos);
memcpy(data, pending.data() + pos, n);
pos += n;
return n;
}
};
/**
* Write as chunks in the format expected by FramedSource.
*
* The exception_ptr reference can be used to terminate the stream when you
* detect that an error has occurred on the remote end.
*/
struct FramedSink : nix::BufferedSink
{
BufferedSink & to;
std::exception_ptr & ex;
FramedSink(BufferedSink & to, std::exception_ptr & ex) : to(to), ex(ex)
{ }
~FramedSink()
{
try {
to << 0;
to.flush();
} catch (...) {
ignoreExceptionInDestructor();
}
}
void writeUnbuffered(std::string_view data) override
{
/* Don't send more data if the remote has
encountered an error. */
if (ex) {
auto ex2 = ex;
ex = nullptr;
std::rethrow_exception(ex2);
}
to << data.size();
to(data);
};
};
/* Disabling GC when entering a coroutine (without the boehm patch).
mutable to avoid boehm gc dependency in libutil.
*/
extern std::shared_ptr<void> (*create_coro_gc_hook)();
}
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