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/ADT/STLExtras.h"
20 #include "llvm/Support/FileSystem.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 {
~DataStreamer()47 DataStreamer::~DataStreamer() {}
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:
DataFileStreamer()57 DataFileStreamer() : Fd(0) {}
~DataFileStreamer()58 ~DataFileStreamer() override { close(Fd); }
GetBytes(unsigned char * buf,size_t len)59 size_t GetBytes(unsigned char *buf, size_t len) override {
60 NumStreamFetches++;
61 return read(Fd, buf, len);
62 }
63
OpenFile(const std::string & Filename)64 std::error_code OpenFile(const std::string &Filename) {
65 if (Filename == "-") {
66 Fd = 0;
67 sys::ChangeStdinToBinary();
68 return std::error_code();
69 }
70
71 return sys::fs::openFileForRead(Filename, Fd);
72 }
73 };
74
75 }
76
77 std::unique_ptr<DataStreamer>
getDataFileStreamer(const std::string & Filename,std::string * StrError)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 }
87