initial commit, 4.5 stable

thirdparty/icu4c/common/unicode/bytestream.h

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+// © 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"
+
+#if U_SHOW_CPLUSPLUS_API
+
+#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;
+
+  /**
+   * Appends n bytes to this. Same as Append().
+   * Call AppendU8() with u8"string literals" which are const char * in C++11
+   * but const char8_t * in C++20.
+   * If the compiler does support char8_t as a distinct type,
+   * then an AppendU8() overload for that is defined and will be chosen.
+   *
+   * @param bytes the pointer to the bytes
+   * @param n the number of bytes; must be non-negative
+   * @stable ICU 67
+   */
+  inline void AppendU8(const char* bytes, int32_t n) {
+    Append(bytes, n);
+  }
+
+#if defined(__cpp_char8_t) || defined(U_IN_DOXYGEN)
+  /**
+   * Appends n bytes to this. Same as Append() but for a const char8_t * pointer.
+   * Call AppendU8() with u8"string literals" which are const char * in C++11
+   * but const char8_t * in C++20.
+   * If the compiler does support char8_t as a distinct type,
+   * then this AppendU8() overload for that is defined and will be chosen.
+   *
+   * @param bytes the pointer to the bytes
+   * @param n the number of bytes; must be non-negative
+   * @stable ICU 67
+   */
+  inline void AppendU8(const char8_t* bytes, int32_t n) {
+    Append(reinterpret_cast<const char*>(bytes), n);
+  }
+#endif
+
+  /**
+   * 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 &) = delete;
+  ByteSink &operator=(const ByteSink &) = delete;
+};
+
+// -------------------------------------------------------------
+// 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) override;
+  /**
+   * 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) override;
+  /**
+   * 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() = delete;
+  CheckedArrayByteSink(const CheckedArrayByteSink &) = delete;
+  CheckedArrayByteSink &operator=(const CheckedArrayByteSink &) = delete;
+};
+
+/** 
+ * 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) { }
+  /**
+   * Constructs a ByteSink that reserves append capacity and will append bytes to the dest string.
+   * 
+   * @param dest pointer to string object to append to
+   * @param initialAppendCapacity capacity beyond dest->length() to be reserve()d
+   * @stable ICU 60
+   */
+  StringByteSink(StringClass* dest, int32_t initialAppendCapacity) : dest_(dest) {
+    if (initialAppendCapacity > 0 &&
+        static_cast<uint32_t>(initialAppendCapacity) > dest->capacity() - dest->length()) {
+      dest->reserve(dest->length() + initialAppendCapacity);
+    }
+  }
+  /**
+   * 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) override { dest_->append(data, n); }
+ private:
+  StringClass* dest_;
+
+  StringByteSink() = delete;
+  StringByteSink(const StringByteSink &) = delete;
+  StringByteSink &operator=(const StringByteSink &) = delete;
+};
+
+U_NAMESPACE_END
+
+#endif /* U_SHOW_CPLUSPLUS_API */
+
+#endif  // __BYTESTREAM_H__