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
30 using namespace llvm;
31
32 #define DEBUG_TYPE "Data-stream"
33
34 // Interface goals:
35 // * StreamingMemoryObject 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 // StreamingMemoryObject 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
45 STATISTIC(NumStreamFetches, "Number of calls to Data stream fetch");
46
47 namespace llvm {
~DataStreamer()48 DataStreamer::~DataStreamer() {}
49 }
50
51 namespace {
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.
55 class DataFileStreamer : public DataStreamer {
56 int Fd;
57 public:
DataFileStreamer()58 DataFileStreamer() : Fd(0) {}
~DataFileStreamer()59 virtual ~DataFileStreamer() {
60 close(Fd);
61 }
GetBytes(unsigned char * buf,size_t len)62 size_t GetBytes(unsigned char *buf, size_t len) override {
63 NumStreamFetches++;
64 return read(Fd, buf, len);
65 }
66
OpenFile(const std::string & Filename)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
80 namespace llvm {
getDataFileStreamer(const std::string & Filename,std::string * StrError)81 DataStreamer *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