LLVM  3.7.0
DataStream.cpp
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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 
18 #include "llvm/ADT/Statistic.h"
19 #include "llvm/ADT/STLExtras.h"
21 #include "llvm/Support/Program.h"
22 #include <string>
23 #include <system_error>
24 #if !defined(_MSC_VER) && !defined(__MINGW32__)
25 #include <unistd.h>
26 #else
27 #include <io.h>
28 #endif
29 using namespace llvm;
30 
31 #define DEBUG_TYPE "Data-stream"
32 
33 // Interface goals:
34 // * StreamingMemoryObject 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 // StreamingMemoryObject 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 
44 STATISTIC(NumStreamFetches, "Number of calls to Data stream fetch");
45 
46 namespace llvm {
48 }
49 
50 namespace {
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.
54 class DataFileStreamer : public DataStreamer {
55  int Fd;
56 public:
57  DataFileStreamer() : Fd(0) {}
58  ~DataFileStreamer() override { close(Fd); }
59  size_t GetBytes(unsigned char *buf, size_t len) override {
60  NumStreamFetches++;
61  return read(Fd, buf, len);
62  }
63 
64  std::error_code OpenFile(const std::string &Filename) {
65  if (Filename == "-") {
66  Fd = 0;
68  return std::error_code();
69  }
70 
71  return sys::fs::openFileForRead(Filename, Fd);
72  }
73 };
74 
75 }
76 
77 std::unique_ptr<DataStreamer>
78 llvm::getDataFileStreamer(const std::string &Filename, std::string *StrError) {
79  std::unique_ptr<DataFileStreamer> s = make_unique<DataFileStreamer>();
80  if (std::error_code e = s->OpenFile(Filename)) {
81  *StrError = std::string("Could not open ") + Filename + ": " +
82  e.message() + "\n";
83  return nullptr;
84  }
85  return std::move(s);
86 }
STATISTIC(NumFunctions,"Total number of functions")
value_type read(const void *memory)
Read a value of a particular endianness from memory.
Definition: Endian.h:49
std::string StrError()
Returns a string representation of the errno value, using whatever thread-safe variant of strerror() ...
Definition: Errno.cpp:32
virtual size_t GetBytes(unsigned char *buf, size_t len)=0
Fetch bytes [start-end) from the stream, and write them to the buffer pointed to by buf...
virtual ~DataStreamer()
Definition: DataStream.cpp:47
std::error_code ChangeStdinToBinary()
std::error_code openFileForRead(const Twine &Name, int &ResultFD)
std::unique_ptr< DataStreamer > getDataFileStreamer(const std::string &Filename, std::string *Err)
Definition: DataStream.cpp:78