lix/src/libutil/serialise.hh

#ifndef __SERIALISE_H
#define __SERIALISE_H

#include "types.hh"


namespace nix {


/* Abstract destination of binary data. */
struct Sink 
{
    virtual ~Sink() { }
    virtual void operator () (const unsigned char * data, size_t len) = 0;
};


/* A buffered abstract sink. */
struct BufferedSink : Sink
{
    size_t bufSize, bufPos;
    unsigned char * buffer;

    BufferedSink(size_t bufSize = 32 * 1024)
        : bufSize(bufSize), bufPos(0), buffer(0) { }
    ~BufferedSink();
    
    void operator () (const unsigned char * data, size_t len);
    
    void flush();
    
    virtual void write(const unsigned char * data, size_t len) = 0;
};


/* Abstract source of binary data. */
struct Source
{
    virtual ~Source() { }
    
    /* Store exactly ‘len’ bytes in the buffer pointed to by ‘data’.
       It blocks if that much data is not yet available, or throws an
       error if it is not going to be available. */
    virtual void operator () (unsigned char * data, size_t len) = 0;
};


/* A buffered abstract source. */
struct BufferedSource : Source
{
    size_t bufSize, bufPosIn, bufPosOut;
    unsigned char * buffer;

    BufferedSource(size_t bufSize = 32 * 1024)
        : bufSize(bufSize), bufPosIn(0), bufPosOut(0), buffer(0) { }
    ~BufferedSource();
    
    void operator () (unsigned char * data, size_t len);
    
    /* Store up to ‘len’ in the buffer pointed to by ‘data’, and
       return the number of bytes stored.  If should block until at
       least one byte is available. */
    virtual size_t read(unsigned char * data, size_t len) = 0;
};


/* A sink that writes data to a file descriptor. */
struct FdSink : BufferedSink
{
    int fd;

    FdSink() : fd(-1) { }
    FdSink(int fd) : fd(fd) { }
    ~FdSink() { flush(); }
    
    void write(const unsigned char * data, size_t len);
};


/* A source that reads data from a file descriptor. */
struct FdSource : BufferedSource
{
    int fd;
    FdSource() : fd(-1) { }
    FdSource(int fd) : fd(fd) { }
    size_t read(unsigned char * data, size_t len);
};


/* A sink that writes data to a string. */
struct StringSink : Sink
{
    string s;
    void operator () (const unsigned char * data, size_t len)
    {
        s.append((const char *) data, len);
    }
};


/* 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) { }
    virtual void operator () (unsigned char * data, size_t len)
    {
        s.copy((char *) data, len, pos);
        pos += len;
        if (pos > s.size())
            throw Error("end of string reached");
    }
};


void writePadding(size_t len, Sink & sink);
void writeInt(unsigned int n, Sink & sink);
void writeLongLong(unsigned long long n, Sink & sink);
void writeString(const string & s, Sink & sink);
void writeStringSet(const StringSet & ss, Sink & sink);

void readPadding(size_t len, Source & source);
unsigned int readInt(Source & source);
unsigned long long readLongLong(Source & source);
string readString(Source & source);
StringSet readStringSet(Source & source);


MakeError(SerialisationError, Error)


}


#endif /* !__SERIALISE_H */