/*
* DataSource
* (C) 1999-2007 Jack Lloyd
*     2005 Matthew Gregan
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/data_src.h>
#include <botan/exceptn.h>
#include <algorithm>
#include <istream>

#if defined(BOTAN_TARGET_OS_HAS_FILESYSTEM)
  #include <fstream>
#endif

namespace Botan {

/*
* Read a single byte from the DataSource
*/
size_t DataSource::read_byte(uint8_t& out)
   {
   return read(&out, 1);
   }

/*
* Peek a single byte from the DataSource
*/
size_t DataSource::peek_byte(uint8_t& out) const
   {
   return peek(&out, 1, 0);
   }

/*
* Discard the next N bytes of the data
*/
size_t DataSource::discard_next(size_t n)
   {
   uint8_t buf[64] = { 0 };
   size_t discarded = 0;

   while(n)
      {
      const size_t got = this->read(buf, std::min(n, sizeof(buf)));
      discarded += got;
      n -= got;

      if(got == 0)
         break;
      }

   return discarded;
   }

/*
* Read from a memory buffer
*/
size_t DataSource_Memory::read(uint8_t out[], size_t length)
   {
   const size_t got = std::min<size_t>(m_source.size() - m_offset, length);
   copy_mem(out, m_source.data() + m_offset, got);
   m_offset += got;
   return got;
   }

bool DataSource_Memory::check_available(size_t n)
   {
   return (n <= (m_source.size() - m_offset));
   }

/*
* Peek into a memory buffer
*/
size_t DataSource_Memory::peek(uint8_t out[], size_t length,
                               size_t peek_offset) const
   {
   const size_t bytes_left = m_source.size() - m_offset;
   if(peek_offset >= bytes_left) return 0;

   const size_t got = std::min(bytes_left - peek_offset, length);
   copy_mem(out, &m_source[m_offset + peek_offset], got);
   return got;
   }

/*
* Check if the memory buffer is empty
*/
bool DataSource_Memory::end_of_data() const
   {
   return (m_offset == m_source.size());
   }

/*
* DataSource_Memory Constructor
*/
DataSource_Memory::DataSource_Memory(const std::string& in) :
   m_source(cast_char_ptr_to_uint8(in.data()),
            cast_char_ptr_to_uint8(in.data()) + in.length()),
   m_offset(0)
   {
   }

/*
* Read from a stream
*/
size_t DataSource_Stream::read(uint8_t out[], size_t length)
   {
   m_source.read(cast_uint8_ptr_to_char(out), length);
   if(m_source.bad())
      throw Stream_IO_Error("DataSource_Stream::read: Source failure");

   const size_t got = static_cast<size_t>(m_source.gcount());
   m_total_read += got;
   return got;
   }

bool DataSource_Stream::check_available(size_t n)
   {
   const std::streampos orig_pos = m_source.tellg();
   m_source.seekg(0, std::ios::end);
   const size_t avail = static_cast<size_t>(m_source.tellg() - orig_pos);
   m_source.seekg(orig_pos);
   return (avail >= n);
   }

/*
* Peek into a stream
*/
size_t DataSource_Stream::peek(uint8_t out[], size_t length, size_t offset) const
   {
   if(end_of_data())
      throw Invalid_State("DataSource_Stream: Cannot peek when out of data");

   size_t got = 0;

   if(offset)
      {
      secure_vector<uint8_t> buf(offset);
      m_source.read(cast_uint8_ptr_to_char(buf.data()), buf.size());
      if(m_source.bad())
         throw Stream_IO_Error("DataSource_Stream::peek: Source failure");
      got = static_cast<size_t>(m_source.gcount());
      }

   if(got == offset)
      {
      m_source.read(cast_uint8_ptr_to_char(out), length);
      if(m_source.bad())
         throw Stream_IO_Error("DataSource_Stream::peek: Source failure");
      got = static_cast<size_t>(m_source.gcount());
      }

   if(m_source.eof())
      m_source.clear();
   m_source.seekg(m_total_read, std::ios::beg);

   return got;
   }

/*
* Check if the stream is empty or in error
*/
bool DataSource_Stream::end_of_data() const
   {
   return (!m_source.good());
   }

/*
* Return a human-readable ID for this stream
*/
std::string DataSource_Stream::id() const
   {
   return m_identifier;
   }

#if defined(BOTAN_TARGET_OS_HAS_FILESYSTEM)

/*
* DataSource_Stream Constructor
*/
DataSource_Stream::DataSource_Stream(const std::string& path,
                                     bool use_binary) :
   m_identifier(path),
   m_source_memory(new std::ifstream(path, use_binary ? std::ios::binary : std::ios::in)),
   m_source(*m_source_memory),
   m_total_read(0)
   {
   if(!m_source.good())
      {
      throw Stream_IO_Error("DataSource: Failure opening file " + path);
      }
   }

#endif

/*
* DataSource_Stream Constructor
*/
DataSource_Stream::DataSource_Stream(std::istream& in,
                                     const std::string& name) :
   m_identifier(name),
   m_source(in),
   m_total_read(0)
   {
   }

DataSource_Stream::~DataSource_Stream()
   {
   // for ~unique_ptr
   }

}