path: root/src/libutil/serialise.hh

#pragma once

#include <memory>

#include "types.hh"
#include "util.hh"

namespace boost::context { struct stack_context; }

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
    { }
};

/* 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();

    virtual void write(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. */
    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;
    bool warn = false;
    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;
        warn = s.warn;
        written = s.written;
        return *this;
    }

    ~FdSink();

    void write(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;

    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
{
    ref<std::string> s;
    StringSink() : s(make_ref<std::string>()) { };
    explicit StringSink(const size_t reservedSize) : s(make_ref<std::string>()) {
      s->reserve(reservedSize);
    };
    StringSink(ref<std::string> s) : s(s) { };
    void operator () (std::string_view data) override;
};


/* A source that reads data from a string. */
struct StringSource : Source
{
    const string & s;
    size_t pos;
    StringSource(const string & _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)
    {
        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)
    {
        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)
    {
        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<