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authorMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
committerMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
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+// Copyright (C) 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+// Copyright (C) 2009-2012, International Business Machines
+// Corporation and others. All Rights Reserved.
+//
+// Copyright 2007 Google Inc. All Rights Reserved.
+// Author: sanjay@google.com (Sanjay Ghemawat)
+//
+// Abstract interface that consumes a sequence of bytes (ByteSink).
+//
+// Used so that we can write a single piece of code that can operate
+// on a variety of output string types.
+//
+// Various implementations of this interface are provided:
+// ByteSink:
+// CheckedArrayByteSink Write to a flat array, with bounds checking
+// StringByteSink Write to an STL string
+
+// This code is a contribution of Google code, and the style used here is
+// a compromise between the original Google code and the ICU coding guidelines.
+// For example, data types are ICU-ified (size_t,int->int32_t),
+// and API comments doxygen-ified, but function names and behavior are
+// as in the original, if possible.
+// Assertion-style error handling, not available in ICU, was changed to
+// parameter "pinning" similar to UnicodeString.
+//
+// In addition, this is only a partial port of the original Google code,
+// limited to what was needed so far. The (nearly) complete original code
+// is in the ICU svn repository at icuhtml/trunk/design/strings/contrib
+// (see ICU ticket 6765, r25517).
+
+#ifndef __BYTESTREAM_H__
+#define __BYTESTREAM_H__
+
+/**
+ * \file
+ * \brief C++ API: Interface for writing bytes, and implementation classes.
+ */
+
+#include "unicode/utypes.h"
+#include "unicode/uobject.h"
+#include "unicode/std_string.h"
+
+U_NAMESPACE_BEGIN
+
+/**
+ * A ByteSink can be filled with bytes.
+ * @stable ICU 4.2
+ */
+class U_COMMON_API ByteSink : public UMemory {
+public:
+ /**
+ * Default constructor.
+ * @stable ICU 4.2
+ */
+ ByteSink() { }
+ /**
+ * Virtual destructor.
+ * @stable ICU 4.2
+ */
+ virtual ~ByteSink();
+
+ /**
+ * Append "bytes[0,n-1]" to this.
+ * @param bytes the pointer to the bytes
+ * @param n the number of bytes; must be non-negative
+ * @stable ICU 4.2
+ */
+ virtual void Append(const char* bytes, int32_t n) = 0;
+
+ /**
+ * Returns a writable buffer for appending and writes the buffer's capacity to
+ * *result_capacity. Guarantees *result_capacity>=min_capacity.
+ * May return a pointer to the caller-owned scratch buffer which must have
+ * scratch_capacity>=min_capacity.
+ * The returned buffer is only valid until the next operation
+ * on this ByteSink.
+ *
+ * After writing at most *result_capacity bytes, call Append() with the
+ * pointer returned from this function and the number of bytes written.
+ * Many Append() implementations will avoid copying bytes if this function
+ * returned an internal buffer.
+ *
+ * Partial usage example:
+ * int32_t capacity;
+ * char* buffer = sink->GetAppendBuffer(..., &capacity);
+ * ... Write n bytes into buffer, with n <= capacity.
+ * sink->Append(buffer, n);
+ * In many implementations, that call to Append will avoid copying bytes.
+ *
+ * If the ByteSink allocates or reallocates an internal buffer, it should use
+ * the desired_capacity_hint if appropriate.
+ * If a caller cannot provide a reasonable guess at the desired capacity,
+ * it should pass desired_capacity_hint=0.
+ *
+ * If a non-scratch buffer is returned, the caller may only pass
+ * a prefix to it to Append().
+ * That is, it is not correct to pass an interior pointer to Append().
+ *
+ * The default implementation always returns the scratch buffer.
+ *
+ * @param min_capacity required minimum capacity of the returned buffer;
+ * must be non-negative
+ * @param desired_capacity_hint desired capacity of the returned buffer;
+ * must be non-negative
+ * @param scratch default caller-owned buffer
+ * @param scratch_capacity capacity of the scratch buffer
+ * @param result_capacity pointer to an integer which will be set to the
+ * capacity of the returned buffer
+ * @return a buffer with *result_capacity>=min_capacity
+ * @stable ICU 4.2
+ */
+ virtual char* GetAppendBuffer(int32_t min_capacity,
+ int32_t desired_capacity_hint,
+ char* scratch, int32_t scratch_capacity,
+ int32_t* result_capacity);
+
+ /**
+ * Flush internal buffers.
+ * Some byte sinks use internal buffers or provide buffering
+ * and require calling Flush() at the end of the stream.
+ * The ByteSink should be ready for further Append() calls after Flush().
+ * The default implementation of Flush() does nothing.
+ * @stable ICU 4.2
+ */
+ virtual void Flush();
+
+private:
+ ByteSink(const ByteSink &); // copy constructor not implemented
+ ByteSink &operator=(const ByteSink &); // assignment operator not implemented
+};
+
+// -------------------------------------------------------------
+// Some standard implementations
+
+/**
+ * Implementation of ByteSink that writes to a flat byte array,
+ * with bounds-checking:
+ * This sink will not write more than capacity bytes to outbuf.
+ * If more than capacity bytes are Append()ed, then excess bytes are ignored,
+ * and Overflowed() will return true.
+ * Overflow does not cause a runtime error.
+ * @stable ICU 4.2
+ */
+class U_COMMON_API CheckedArrayByteSink : public ByteSink {
+public:
+ /**
+ * Constructs a ByteSink that will write to outbuf[0..capacity-1].
+ * @param outbuf buffer to write to
+ * @param capacity size of the buffer
+ * @stable ICU 4.2
+ */
+ CheckedArrayByteSink(char* outbuf, int32_t capacity);
+ /**
+ * Destructor.
+ * @stable ICU 4.2
+ */
+ virtual ~CheckedArrayByteSink();
+ /**
+ * Returns the sink to its original state, without modifying the buffer.
+ * Useful for reusing both the buffer and the sink for multiple streams.
+ * Resets the state to NumberOfBytesWritten()=NumberOfBytesAppended()=0
+ * and Overflowed()=FALSE.
+ * @return *this
+ * @stable ICU 4.6
+ */
+ virtual CheckedArrayByteSink& Reset();
+ /**
+ * Append "bytes[0,n-1]" to this.
+ * @param bytes the pointer to the bytes
+ * @param n the number of bytes; must be non-negative
+ * @stable ICU 4.2
+ */
+ virtual void Append(const char* bytes, int32_t n);
+ /**
+ * Returns a writable buffer for appending and writes the buffer's capacity to
+ * *result_capacity. For details see the base class documentation.
+ * @param min_capacity required minimum capacity of the returned buffer;
+ * must be non-negative
+ * @param desired_capacity_hint desired capacity of the returned buffer;
+ * must be non-negative
+ * @param scratch default caller-owned buffer
+ * @param scratch_capacity capacity of the scratch buffer
+ * @param result_capacity pointer to an integer which will be set to the
+ * capacity of the returned buffer
+ * @return a buffer with *result_capacity>=min_capacity
+ * @stable ICU 4.2
+ */
+ virtual char* GetAppendBuffer(int32_t min_capacity,
+ int32_t desired_capacity_hint,
+ char* scratch, int32_t scratch_capacity,
+ int32_t* result_capacity);
+ /**
+ * Returns the number of bytes actually written to the sink.
+ * @return number of bytes written to the buffer
+ * @stable ICU 4.2
+ */
+ int32_t NumberOfBytesWritten() const { return size_; }
+ /**
+ * Returns true if any bytes were discarded, i.e., if there was an
+ * attempt to write more than 'capacity' bytes.
+ * @return TRUE if more than 'capacity' bytes were Append()ed
+ * @stable ICU 4.2
+ */
+ UBool Overflowed() const { return overflowed_; }
+ /**
+ * Returns the number of bytes appended to the sink.
+ * If Overflowed() then NumberOfBytesAppended()>NumberOfBytesWritten()
+ * else they return the same number.
+ * @return number of bytes written to the buffer
+ * @stable ICU 4.6
+ */
+ int32_t NumberOfBytesAppended() const { return appended_; }
+private:
+ char* outbuf_;
+ const int32_t capacity_;
+ int32_t size_;
+ int32_t appended_;
+ UBool overflowed_;
+ CheckedArrayByteSink(); ///< default constructor not implemented
+ CheckedArrayByteSink(const CheckedArrayByteSink &); ///< copy constructor not implemented
+ CheckedArrayByteSink &operator=(const CheckedArrayByteSink &); ///< assignment operator not implemented
+};
+
+#if U_HAVE_STD_STRING
+
+/**
+ * Implementation of ByteSink that writes to a "string".
+ * The StringClass is usually instantiated with a std::string.
+ * @stable ICU 4.2
+ */
+template<typename StringClass>
+class StringByteSink : public ByteSink {
+ public:
+ /**
+ * Constructs a ByteSink that will append bytes to the dest string.
+ * @param dest pointer to string object to append to
+ * @stable ICU 4.2
+ */
+ StringByteSink(StringClass* dest) : dest_(dest) { }
+ /**
+ * Append "bytes[0,n-1]" to this.
+ * @param data the pointer to the bytes
+ * @param n the number of bytes; must be non-negative
+ * @stable ICU 4.2
+ */
+ virtual void Append(const char* data, int32_t n) { dest_->append(data, n); }
+ private:
+ StringClass* dest_;
+ StringByteSink(); ///< default constructor not implemented
+ StringByteSink(const StringByteSink &); ///< copy constructor not implemented
+ StringByteSink &operator=(const StringByteSink &); ///< assignment operator not implemented
+};
+
+#endif
+
+U_NAMESPACE_END
+
+#endif // __BYTESTREAM_H__