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#include "llvm/Support/DataStream.h"
18#include "llvm/ADT/Statistic.h"
19#include "llvm/Support/FileSystem.h"
20#include "llvm/Support/Program.h"
21#include <cerrno>
22#include <cstdio>
23#include <string>
24#include <system_error>
25#if !defined(_MSC_VER) && !defined(__MINGW32__)
26#include <unistd.h>
27#else
28#include <io.h>
29#endif
30using namespace llvm;
31
32#define DEBUG_TYPE "Data-stream"
33
34// Interface goals:
35// * StreamableMemoryObject doesn't care about complexities like using
36//   threads/async callbacks to actually overlap download+compile
37// * Don't want to duplicate Data in memory
38// * Don't need to know total Data len in advance
39// Non-goals:
40// StreamableMemoryObject already has random access so this interface only does
41// in-order streaming (no arbitrary seeking, else we'd have to buffer all the
42// Data here in addition to MemoryObject).  This also means that if we want
43// to be able to to free Data, BitstreamBytes/BitcodeReader will implement it
44
45STATISTIC(NumStreamFetches, "Number of calls to Data stream fetch");
46
47namespace llvm {
48DataStreamer::~DataStreamer() {}
49}
50
51namespace {
52
53// Very simple stream backed by a file. Mostly useful for stdin and debugging;
54// actual file access is probably still best done with mmap.
55class DataFileStreamer : public DataStreamer {
56 int Fd;
57public:
58  DataFileStreamer() : Fd(0) {}
59  virtual ~DataFileStreamer() {
60    close(Fd);
61  }
62  size_t GetBytes(unsigned char *buf, size_t len) override {
63    NumStreamFetches++;
64    return read(Fd, buf, len);
65  }
66
67  std::error_code OpenFile(const std::string &Filename) {
68    if (Filename == "-") {
69      Fd = 0;
70      sys::ChangeStdinToBinary();
71      return std::error_code();
72    }
73
74    return sys::fs::openFileForRead(Filename, Fd);
75  }
76};
77
78}
79
80namespace llvm {
81DataStreamer *getDataFileStreamer(const std::string &Filename,
82                                  std::string *StrError) {
83  DataFileStreamer *s = new DataFileStreamer();
84  if (std::error_code e = s->OpenFile(Filename)) {
85    *StrError = std::string("Could not open ") + Filename + ": " +
86        e.message() + "\n";
87    return nullptr;
88  }
89  return s;
90}
91
92}
93