DataStream.cpp revision 58604cd944eec4a75046076cb53eb708aaf2ee09 
1//===--- llvm/Support/DataStream.cpp - Lazy streamed data -----------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements DataStreamer, which fetches bytes of Data from
11// a stream source. It provides support for streaming (lazy reading) of
12// bitcode. An example implementation of streaming from a file or stdin
13// is included.
14//
15//===----------------------------------------------------------------------===//
16
17#define DEBUG_TYPE "Data-stream"
18#include "llvm/ADT/Statistic.h"
19#include "llvm/Support/DataStream.h"
20#include "llvm/Support/Program.h"
21#include "llvm/Support/system_error.h"
22#include <string>
23#include <cerrno>
24#include <cstdio>
25#if !defined(_MSC_VER) && !defined(__MINGW32__)
26#include <unistd.h>
27#else
28#include <io.h>
29#endif
30#include <fcntl.h>
31using namespace llvm;
32
33// Interface goals:
34// * StreamableMemoryObject doesn't care about complexities like using
35//   threads/async callbacks to actually overlap download+compile
36// * Don't want to duplicate Data in memory
37// * Don't need to know total Data len in advance
38// Non-goals:
39// StreamableMemoryObject already has random access so this interface only does
40// in-order streaming (no arbitrary seeking, else we'd have to buffer all the
41// Data here in addition to MemoryObject).  This also means that if we want
42// to be able to to free Data, BitstreamBytes/BitcodeReader will implement it
43
44STATISTIC(NumStreamFetches, "Number of calls to Data stream fetch");
45
46namespace llvm {
47DataStreamer::~DataStreamer() {}
48}
49
50namespace {
51
52// Very simple stream backed by a file. Mostly useful for stdin and debugging;
53// actual file access is probably still best done with mmap.
54class DataFileStreamer : public DataStreamer {
55 int Fd;
56public:
57  DataFileStreamer() : Fd(0) {}
58  virtual ~DataFileStreamer() {
59    close(Fd);
60  }
61  virtual size_t GetBytes(unsigned char *buf, size_t len) {
62    NumStreamFetches++;
63    return read(Fd, buf, len);
64  }
65
66  error_code OpenFile(const std::string &Filename) {
67    if (Filename == "-") {
68      Fd = 0;
69      sys::Program::ChangeStdinToBinary();
70      return error_code::success();
71    }
72
73    int OpenFlags = O_RDONLY;
74#ifdef O_BINARY
75    OpenFlags |= O_BINARY;  // Open input file in binary mode on win32.
76#endif
77    Fd = ::open(Filename.c_str(), OpenFlags);
78    if (Fd == -1)
79      return error_code(errno, posix_category());
80    return error_code::success();
81  }
82};
83
84}
85
86namespace llvm {
87DataStreamer *getDataFileStreamer(const std::string &Filename,
88                                  std::string *StrError) {
89  DataFileStreamer *s = new DataFileStreamer();
90  if (error_code e = s->OpenFile(Filename)) {
91    *StrError = std::string("Could not open ") + Filename + ": " +
92        e.message() + "\n";
93    return NULL;
94  }
95  return s;
96}
97
98}
99