comparison osx/include/kj/io.h @ 134:41e769c91eca

Add Capnp and KJ builds for OSX

+// Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
+// Licensed under the MIT License:
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+#ifndef KJ_IO_H_
+#define KJ_IO_H_
+
+#if defined(__GNUC__) && !KJ_HEADER_WARNINGS
+#pragma GCC system_header
+#endif
+
+#include <stddef.h>
+#include "common.h"
+#include "array.h"
+#include "exception.h"
+
+namespace kj {
+
+// =======================================================================================
+// Abstract interfaces
+
+class InputStream {
+public:
+  virtual ~InputStream() noexcept(false);
+
+  size_t read(void* buffer, size_t minBytes, size_t maxBytes);
+  // Reads at least minBytes and at most maxBytes, copying them into the given buffer.  Returns
+  // the size read.  Throws an exception on errors.  Implemented in terms of tryRead().
+  //
+  // maxBytes is the number of bytes the caller really wants, but minBytes is the minimum amount
+  // needed by the caller before it can start doing useful processing.  If the stream returns less
+  // than maxBytes, the caller will usually call read() again later to get the rest.  Returning
+  // less than maxBytes is useful when it makes sense for the caller to parallelize processing
+  // with I/O.
+  //
+  // Never blocks if minBytes is zero.  If minBytes is zero and maxBytes is non-zero, this may
+  // attempt a non-blocking read or may just return zero.  To force a read, use a non-zero minBytes.
+  // To detect EOF without throwing an exception, use tryRead().
+  //
+  // If the InputStream can't produce minBytes, it MUST throw an exception, as the caller is not
+  // expected to understand how to deal with partial reads.
+
+  virtual size_t tryRead(void* buffer, size_t minBytes, size_t maxBytes) = 0;
+  // Like read(), but may return fewer than minBytes on EOF.
+
+  inline void read(void* buffer, size_t bytes) { read(buffer, bytes, bytes); }
+  // Convenience method for reading an exact number of bytes.
+
+  virtual void skip(size_t bytes);
+  // Skips past the given number of bytes, discarding them.  The default implementation read()s
+  // into a scratch buffer.
+};
+
+class OutputStream {
+public:
+  virtual ~OutputStream() noexcept(false);
+
+  virtual void write(const void* buffer, size_t size) = 0;
+  // Always writes the full size.  Throws exception on error.
+
+  virtual void write(ArrayPtr<const ArrayPtr<const byte>> pieces);
+  // Equivalent to write()ing each byte array in sequence, which is what the default implementation
+  // does.  Override if you can do something better, e.g. use writev() to do the write in a single
+  // syscall.
+};
+
+class BufferedInputStream: public InputStream {
+  // An input stream which buffers some bytes in memory to reduce system call overhead.
+  // - OR -
+  // An input stream that actually reads from some in-memory data structure and wants to give its
+  // caller a direct pointer to that memory to potentially avoid a copy.
+
+public:
+  virtual ~BufferedInputStream() noexcept(false);
+
+  ArrayPtr<const byte> getReadBuffer();
+  // Get a direct pointer into the read buffer, which contains the next bytes in the input.  If the
+  // caller consumes any bytes, it should then call skip() to indicate this.  This always returns a
+  // non-empty buffer or throws an exception.  Implemented in terms of tryGetReadBuffer().
+
+  virtual ArrayPtr<const byte> tryGetReadBuffer() = 0;
+  // Like getReadBuffer() but may return an empty buffer on EOF.
+};
+
+class BufferedOutputStream: public OutputStream {
+  // An output stream which buffers some bytes in memory to reduce system call overhead.
+  // - OR -
+  // An output stream that actually writes into some in-memory data structure and wants to give its
+  // caller a direct pointer to that memory to potentially avoid a copy.
+
+public:
+  virtual ~BufferedOutputStream() noexcept(false);
+
+  virtual ArrayPtr<byte> getWriteBuffer() = 0;
+  // Get a direct pointer into the write buffer.  The caller may choose to fill in some prefix of
+  // this buffer and then pass it to write(), in which case write() may avoid a copy.  It is
+  // incorrect to pass to write any slice of this buffer which is not a prefix.
+};
+
+// =======================================================================================
+// Buffered streams implemented as wrappers around regular streams
+
+class BufferedInputStreamWrapper: public BufferedInputStream {
+  // Implements BufferedInputStream in terms of an InputStream.
+  //
+  // Note that the underlying stream's position is unpredictable once the wrapper is destroyed,
+  // unless the entire stream was consumed.  To read a predictable number of bytes in a buffered
+  // way without going over, you'd need this wrapper to wrap some other wrapper which itself
+  // implements an artificial EOF at the desired point.  Such a stream should be trivial to write
+  // but is not provided by the library at this time.
+
+public:
+  explicit BufferedInputStreamWrapper(InputStream& inner, ArrayPtr<byte> buffer = nullptr);
+  // Creates a buffered stream wrapping the given non-buffered stream.  No guarantee is made about
+  // the position of the inner stream after a buffered wrapper has been created unless the entire
+  // input is read.
+  //
+  // If the second parameter is non-null, the stream uses the given buffer instead of allocating
+  // its own.  This may improve performance if the buffer can be reused.
+
+  KJ_DISALLOW_COPY(BufferedInputStreamWrapper);
+  ~BufferedInputStreamWrapper() noexcept(false);
+
+  // implements BufferedInputStream ----------------------------------
+  ArrayPtr<const byte> tryGetReadBuffer() override;
+  size_t tryRead(void* buffer, size_t minBytes, size_t maxBytes) override;
+  void skip(size_t bytes) override;
+
+private:
+  InputStream& inner;
+  Array<byte> ownedBuffer;
+  ArrayPtr<byte> buffer;
+  ArrayPtr<byte> bufferAvailable;
+};
+
+class BufferedOutputStreamWrapper: public BufferedOutputStream {
+  // Implements BufferedOutputStream in terms of an OutputStream.  Note that writes to the
+  // underlying stream may be delayed until flush() is called or the wrapper is destroyed.
+
+public:
+  explicit BufferedOutputStreamWrapper(OutputStream& inner, ArrayPtr<byte> buffer = nullptr);
+  // Creates a buffered stream wrapping the given non-buffered stream.
+  //
+  // If the second parameter is non-null, the stream uses the given buffer instead of allocating
+  // its own.  This may improve performance if the buffer can be reused.
+
+  KJ_DISALLOW_COPY(BufferedOutputStreamWrapper);
+  ~BufferedOutputStreamWrapper() noexcept(false);
+
+  void flush();
+  // Force the wrapper to write any remaining bytes in its buffer to the inner stream.  Note that
+  // this only flushes this object's buffer; this object has no idea how to flush any other buffers
+  // that may be present in the underlying stream.
+
+  // implements BufferedOutputStream ---------------------------------
+  ArrayPtr<byte> getWriteBuffer() override;
+  void write(const void* buffer, size_t size) override;
+
+private:
+  OutputStream& inner;
+  Array<byte> ownedBuffer;
+  ArrayPtr<byte> buffer;
+  byte* bufferPos;
+  UnwindDetector unwindDetector;
+};
+
+// =======================================================================================
+// Array I/O
+
+class ArrayInputStream: public BufferedInputStream {
+public:
+  explicit ArrayInputStream(ArrayPtr<const byte> array);
+  KJ_DISALLOW_COPY(ArrayInputStream);
+  ~ArrayInputStream() noexcept(false);
+
+  // implements BufferedInputStream ----------------------------------
+  ArrayPtr<const byte> tryGetReadBuffer() override;
+  size_t tryRead(void* buffer, size_t minBytes, size_t maxBytes) override;
+  void skip(size_t bytes) override;
+
+private:
+  ArrayPtr<const byte> array;
+};
+
+class ArrayOutputStream: public BufferedOutputStream {
+public:
+  explicit ArrayOutputStream(ArrayPtr<byte> array);
+  KJ_DISALLOW_COPY(ArrayOutputStream);
+  ~ArrayOutputStream() noexcept(false);
+
+  ArrayPtr<byte> getArray() {
+    // Get the portion of the array which has been filled in.
+    return arrayPtr(array.begin(), fillPos);
+  }
+
+  // implements BufferedInputStream ----------------------------------
+  ArrayPtr<byte> getWriteBuffer() override;
+  void write(const void* buffer, size_t size) override;
+
+private:
+  ArrayPtr<byte> array;
+  byte* fillPos;
+};
+
+class VectorOutputStream: public BufferedOutputStream {
+public:
+  explicit VectorOutputStream(size_t initialCapacity = 4096);
+  KJ_DISALLOW_COPY(VectorOutputStream);
+  ~VectorOutputStream() noexcept(false);
+
+  ArrayPtr<byte> getArray() {
+    // Get the portion of the array which has been filled in.
+    return arrayPtr(vector.begin(), fillPos);
+  }
+
+  // implements BufferedInputStream ----------------------------------
+  ArrayPtr<byte> getWriteBuffer() override;
+  void write(const void* buffer, size_t size) override;
+
+private:
+  Array<byte> vector;
+  byte* fillPos;
+
+  void grow(size_t minSize);
+};
+
+// =======================================================================================
+// File descriptor I/O
+
+class AutoCloseFd {
+  // A wrapper around a file descriptor which automatically closes the descriptor when destroyed.
+  // The wrapper supports move construction for transferring ownership of the descriptor.  If
+  // close() returns an error, the destructor throws an exception, UNLESS the destructor is being
+  // called during unwind from another exception, in which case the close error is ignored.
+  //
+  // If your code is not exception-safe, you should not use AutoCloseFd.  In this case you will
+  // have to call close() yourself and handle errors appropriately.
+
+public:
+  inline AutoCloseFd(): fd(-1) {}
+  inline AutoCloseFd(decltype(nullptr)): fd(-1) {}
+  inline explicit AutoCloseFd(int fd): fd(fd) {}
+  inline AutoCloseFd(AutoCloseFd&& other) noexcept: fd(other.fd) { other.fd = -1; }
+  KJ_DISALLOW_COPY(AutoCloseFd);
+  ~AutoCloseFd() noexcept(false);
+
+  inline AutoCloseFd& operator=(AutoCloseFd&& other) {
+    AutoCloseFd old(kj::mv(*this));
+    fd = other.fd;
+    other.fd = -1;
+    return *this;
+  }
+
+  inline AutoCloseFd& operator=(decltype(nullptr)) {
+    AutoCloseFd old(kj::mv(*this));
+    return *this;
+  }
+
+  inline operator int() const { return fd; }
+  inline int get() const { return fd; }
+
+  operator bool() const = delete;
+  // Deleting this operator prevents accidental use in boolean contexts, which
+  // the int conversion operator above would otherwise allow.
+
+  inline bool operator==(decltype(nullptr)) { return fd < 0; }
+  inline bool operator!=(decltype(nullptr)) { return fd >= 0; }
+
+private:
+  int fd;
+  UnwindDetector unwindDetector;
+};
+
+inline auto KJ_STRINGIFY(const AutoCloseFd& fd)
+    -> decltype(kj::toCharSequence(implicitCast<int>(fd))) {
+  return kj::toCharSequence(implicitCast<int>(fd));
+}
+
+class FdInputStream: public InputStream {
+  // An InputStream wrapping a file descriptor.
+
+public:
+  explicit FdInputStream(int fd): fd(fd) {}
+  explicit FdInputStream(AutoCloseFd fd): fd(fd), autoclose(mv(fd)) {}
+  KJ_DISALLOW_COPY(FdInputStream);
+  ~FdInputStream() noexcept(false);
+
+  size_t tryRead(void* buffer, size_t minBytes, size_t maxBytes) override;
+
+private:
+  int fd;
+  AutoCloseFd autoclose;
+};
+
+class FdOutputStream: public OutputStream {
+  // An OutputStream wrapping a file descriptor.
+
+public:
+  explicit FdOutputStream(int fd): fd(fd) {}
+  explicit FdOutputStream(AutoCloseFd fd): fd(fd), autoclose(mv(fd)) {}
+  KJ_DISALLOW_COPY(FdOutputStream);
+  ~FdOutputStream() noexcept(false);
+
+  void write(const void* buffer, size_t size) override;
+  void write(ArrayPtr<const ArrayPtr<const byte>> pieces) override;
+
+private:
+  int fd;
+  AutoCloseFd autoclose;
+};
+
+}  // namespace kj
+
+#endif  // KJ_IO_H_