Add IO utilities.

* Add fixed size stream for reading model stream.
* Add file extension.

src/common/io.cc

@@ -1,20 +1,97 @@
 /*!
- * Copyright (c) by Contributors 2019
+ * Copyright (c) by XGBoost Contributors 2019
  */
 #if defined(__unix__)
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <unistd.h>
 #endif  // defined(__unix__)
+#include <algorithm>
 #include <cstdio>
 #include <string>
+#include <utility>
 
 #include "xgboost/logging.h"
 #include "io.h"
 
 namespace xgboost {
 namespace common {
 
+size_t PeekableInStream::Read(void* dptr, size_t size) {
+  size_t nbuffer = buffer_.length() - buffer_ptr_;
+  if (nbuffer == 0) return strm_->Read(dptr, size);
+  if (nbuffer < size) {
+    std::memcpy(dptr, dmlc::BeginPtr(buffer_) + buffer_ptr_, nbuffer);
+    buffer_ptr_ += nbuffer;
+    return nbuffer + strm_->Read(reinterpret_cast<char*>(dptr) + nbuffer,
+                                 size - nbuffer);
+  } else {
+    std::memcpy(dptr, dmlc::BeginPtr(buffer_) + buffer_ptr_, size);
+    buffer_ptr_ += size;
+    return size;
+  }
+}
+
+size_t PeekableInStream::PeekRead(void* dptr, size_t size) {
+  size_t nbuffer = buffer_.length() - buffer_ptr_;
+  if (nbuffer < size) {
+    buffer_ = buffer_.substr(buffer_ptr_, buffer_.length());
+    buffer_ptr_ = 0;
+    buffer_.resize(size);
+    size_t nadd = strm_->Read(dmlc::BeginPtr(buffer_) + nbuffer, size - nbuffer);
+    buffer_.resize(nbuffer + nadd);
+    std::memcpy(dptr, dmlc::BeginPtr(buffer_), buffer_.length());
+    return buffer_.size();
+  } else {
+    std::memcpy(dptr, dmlc::BeginPtr(buffer_) + buffer_ptr_, size);
+    return size;
+  }
+}
+
+FixedSizeStream::FixedSizeStream(PeekableInStream* stream) : PeekableInStream(stream), pointer_{0} {
+  size_t constexpr kInitialSize = 4096;
+  size_t size {kInitialSize}, total {0};
+  buffer_.clear();
+  while (true) {
+    buffer_.resize(size);
+    size_t read = stream->PeekRead(&buffer_[0], size);
+    total = read;
+    if (read < size) {
+      break;
+    }
+    size *= 2;
+  }
+  buffer_.resize(total);
+}
+
+size_t FixedSizeStream::Read(void* dptr, size_t size) {
+  auto read = this->PeekRead(dptr, size);
+  pointer_ += read;
+  return read;
+}
+
+size_t FixedSizeStream::PeekRead(void* dptr, size_t size) {
+  if (size >= buffer_.size() - pointer_)  {
+    std::copy(buffer_.cbegin() + pointer_, buffer_.cend(), reinterpret_cast<char*>(dptr));
+    return std::distance(buffer_.cbegin() + pointer_, buffer_.cend());
+  } else {
+    auto const beg = buffer_.cbegin() + pointer_;
+    auto const end = beg + size;
+    std::copy(beg, end, reinterpret_cast<char*>(dptr));
+    return std::distance(beg, end);
+  }
+}
+
+void FixedSizeStream::Seek(size_t pos) {
+  pointer_ = pos;
+  CHECK_LE(pointer_, buffer_.size());
+}
+
+void FixedSizeStream::Take(std::string* out) {
+  CHECK(out);
+  *out = std::move(buffer_);
+}
+
 std::string LoadSequentialFile(std::string fname) {
   auto OpenErr = [&fname]() {
                    std::string msg;
@@ -59,6 +136,7 @@ std::string LoadSequentialFile(std::string fname) {
 
   buffer.resize(fsize + 1);
   fread(&buffer[0], 1, fsize, f);
+  buffer.back() = '\0';
   fclose(f);
 #endif  // defined(__unix__)
   return buffer;

src/common/io.h

@@ -13,6 +13,8 @@
 #include <string>
 #include <cstring>
 
+#include "common.h"
+
 namespace xgboost {
 namespace common {
 using MemoryFixSizeBuffer = rabit::utils::MemoryFixSizeBuffer;
@@ -27,36 +29,8 @@ class PeekableInStream : public dmlc::Stream {
   explicit PeekableInStream(dmlc::Stream* strm)
       : strm_(strm), buffer_ptr_(0) {}
 
-  size_t Read(void* dptr, size_t size) override {
-    size_t nbuffer = buffer_.length() - buffer_ptr_;
-    if (nbuffer == 0) return strm_->Read(dptr, size);
-    if (nbuffer < size) {
-      std::memcpy(dptr, dmlc::BeginPtr(buffer_) + buffer_ptr_, nbuffer);
-      buffer_ptr_ += nbuffer;
-      return nbuffer + strm_->Read(reinterpret_cast<char*>(dptr) + nbuffer,
-                                   size - nbuffer);
-    } else {
-      std::memcpy(dptr, dmlc::BeginPtr(buffer_) + buffer_ptr_, size);
-      buffer_ptr_ += size;
-      return size;
-    }
-  }
-
-  size_t PeekRead(void* dptr, size_t size) {
-    size_t nbuffer = buffer_.length() - buffer_ptr_;
-    if (nbuffer < size) {
-      buffer_ = buffer_.substr(buffer_ptr_, buffer_.length());
-      buffer_ptr_ = 0;
-      buffer_.resize(size);
-      size_t nadd = strm_->Read(dmlc::BeginPtr(buffer_) + nbuffer, size - nbuffer);
-      buffer_.resize(nbuffer + nadd);
-      std::memcpy(dptr, dmlc::BeginPtr(buffer_), buffer_.length());
-      return buffer_.length();
-    } else {
-      std::memcpy(dptr, dmlc::BeginPtr(buffer_) + buffer_ptr_, size);
-      return size;
-    }
-  }
+  size_t Read(void* dptr, size_t size) override;
+  virtual size_t PeekRead(void* dptr, size_t size);
 
   void Write(const void* dptr, size_t size) override {
     LOG(FATAL) << "Not implemented";
@@ -71,9 +45,40 @@ class PeekableInStream : public dmlc::Stream {
   std::string buffer_;
 };
 
+class FixedSizeStream : public PeekableInStream {
+ public:
+  explicit FixedSizeStream(PeekableInStream* stream);
+  ~FixedSizeStream() = default;
+
+  size_t Read(void* dptr, size_t size) override;
+  size_t PeekRead(void* dptr, size_t size) override;
+  size_t Size() const { return buffer_.size(); }
+  size_t Tell() const { return pointer_; }
+  void Seek(size_t pos);
+
+  void Write(const void* dptr, size_t size) override {
+    LOG(FATAL) << "Not implemented";
+  }
+
+  void Take(std::string* out);
+
+ private:
+  size_t pointer_;
+  std::string buffer_;
+};
+
 // Optimized for consecutive file loading in unix like systime.
 std::string LoadSequentialFile(std::string fname);
 
+inline std::string FileExtension(std::string const& fname) {
+  auto splited = Split(fname, '.');
+  if (splited.size() > 1) {
+    return splited.back();
+  } else {
+    return "";
+  }
+}
+
 }  // namespace common
 }  // namespace xgboost
 #endif  // XGBOOST_COMMON_IO_H_

tests/cpp/common/test_io.cc

@@ -0,0 +1,43 @@
+/*!
+ * Copyright (c) by XGBoost Contributors 2019
+ */
+#include <gtest/gtest.h>
+#include "../../../src/common/io.h"
+
+namespace xgboost {
+namespace common {
+TEST(IO, FileExtension) {
+  std::string filename {u8"model.json"};
+  auto ext = FileExtension(filename);
+  ASSERT_EQ(ext, u8"json");
+}
+
+TEST(IO, FixedSizeStream) {
+  std::string buffer {"This is the content of stream"};
+  {
+    MemoryFixSizeBuffer stream((void *)buffer.c_str(), buffer.size());
+    PeekableInStream peekable(&stream);
+    FixedSizeStream fixed(&peekable);
+
+    std::string out_buffer;
+    fixed.Take(&out_buffer);
+    ASSERT_EQ(buffer, out_buffer);
+  }
+
+  {
+    std::string huge_buffer;
+    for (size_t i = 0; i < 512; i++) {
+      huge_buffer += buffer;
+    }
+
+    MemoryFixSizeBuffer stream((void *)huge_buffer.c_str(), huge_buffer.size());
+    PeekableInStream peekable(&stream);
+    FixedSizeStream fixed(&peekable);
+
+    std::string out_buffer;
+    fixed.Take(&out_buffer);
+    ASSERT_EQ(huge_buffer, out_buffer);
+  }
+}
+}
+}  // namespace xgboost