source/io/slice.cpp

   1 #include <msp/core/except.h>
   2 #include "slice.h"
   3
   4 using namespace std;
   5
   6 namespace Msp {
   7 namespace IO {
   8
   9 Slice::Slice(Seekable &b, SeekOffset s, SeekOffset l):
  10         below(b),
  11         start_offset(s),
  12         length(l)
  13 {
  14         if(s<0 || l<0)
  15                 throw invalid_argument("Slice::Slice");
  16
  17         Base::Synchronize sync(below);
  18         mode = below.get_mode()&M_RDWR;
  19         below.signal_flush_required.connect(sigc::mem_fun(this, &Slice::flush));
  20 }
  21
  22 void Slice::set_block(bool)
  23 {
  24         throw unsupported("Slice::set_block");
  25 }
  26
  27 void Slice::set_inherit(bool)
  28 {
  29         throw unsupported("Slice::set_inherit");
  30 }
  31
  32 void Slice::flush()
  33 {
  34         sync_position = true;
  35 }
  36
  37 unsigned Slice::prepare_op(unsigned size, Mode m)
  38 {
  39         check_access(m);
  40
  41         if(sync_position)
  42         {
  43                 SeekOffset pos = below.seek(start_offset+position, S_BEG)-start_offset;
  44                 if(pos!=position)
  45                         throw runtime_error("failed to restore position");
  46                 sync_position = false;
  47         }
  48
  49         SeekOffset remaining = length-position;
  50         if(size>remaining)
  51                 size = remaining;
  52         if(!size && m==M_READ)
  53                 set_eof();
  54
  55         return size;
  56 }
  57
  58 size_t Slice::do_write(const char *data, size_t size)
  59 {
  60         Base::Synchronize sync(below);
  61         size = prepare_op(size, M_WRITE);
  62         if(!size)
  63                 return 0;
  64
  65         size_t len = below.write(data, size);
  66         position += len;
  67         return len;
  68 }
  69
  70 size_t Slice::do_read(char *data, size_t size)
  71 {
  72         Base::Synchronize sync(below);
  73         size = prepare_op(size, M_READ);
  74         if(!size)
  75                 return 0;
  76
  77         size_t len = below.read(data, size);
  78         if(!len && below.eof())
  79                 set_eof();
  80         position += len;
  81         return len;
  82 }
  83
  84 size_t Slice::put(char c)
  85 {
  86         Base::Synchronize sync(below);
  87         if(!prepare_op(1, M_WRITE))
  88                 return 0;
  89
  90         size_t len = below.put(c);
  91         position += len;
  92         return len;
  93 }
  94
  95 int Slice::get()
  96 {
  97         Base::Synchronize sync(below);
  98         if(!prepare_op(1, M_READ))
  99                 return -1;
 100
 101         int c = below.get();
 102         if(c==-1 && below.eof())
 103                 set_eof();
 104         else
 105                 ++position;
 106         return c;
 107 }
 108
 109 const Handle &Slice::get_handle(Mode)
 110 {
 111         throw unsupported("Slice::get_handle");
 112 }
 113
 114 SeekOffset Slice::seek(SeekOffset off, SeekType type)
 115 {
 116         Base::Synchronize sync(below);
 117         off += start_offset;
 118         if(type==S_CUR)
 119                 off += position;
 120         else if(type==S_END)
 121                 off += length;
 122         else if(type!=S_BEG)
 123                 throw invalid_argument("Slice::seek");
 124
 125         if(off<start_offset || off>start_offset+length)
 126                 throw bad_seek(off, type);
 127
 128         signal_flush_required.emit();
 129
 130         position = below.seek(off, S_BEG)-start_offset;
 131         sync_position = false;
 132         return position;
 133 }
 134
 135 } // namespace IO
 136 } // namespace Msp