memsrc.cpp

伯克利做的SFTP安全文件传输协议

// memsrc.cc
// code for memsrc.h
// copyright SafeTP Development Group, Inc., 2000  Terms of use are as specified in license.txt

#include "memsrc.h"      // this module
#include <string.h>      // memcpy
#include "xassert.h"     // xassert
#include "typ.h"         // SELFCHECK, min

//#define min(a,b) ((a)<(b)?(a):(b))


MemoryInputSource::MemoryInputSource(char const *D, int L)
  : data(D),
    dataLen(L),
    next(D)
{
  selfCheck();    // check ctor arguments
}


// check invariants
void MemoryInputSource::selfCheck() const
{
  xassert(data != NULL &&
          dataLen >= 0 &&
          0 <= (next-data) &&
               (next-data) <= dataLen);
}


int MemoryInputSource::read(char *buffer, int bufLen)
{
  SELFCHECK();

  // compute # of bytes to copy
  int rem = remaining();
  int supply = mymin(rem, bufLen);

  // copy bytes
  if (supply > 0) {
    memcpy(buffer, next, supply);

    // consume bytes
    next += supply;
  }

  SELFCHECK();
  return supply;
}


int MemoryInputSource::remaining() const
{
  return dataLen - (next-data);
}