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https://git.hardenedbsd.org/hardenedbsd/HardenedBSD.git
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290 lines
8.8 KiB
C++
290 lines
8.8 KiB
C++
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/*-
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* Copyright (c) 2013 David Chisnall
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* All rights reserved.
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*
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* This software was developed by SRI International and the University of
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* Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237)
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* ("CTSRD"), as part of the DARPA CRASH research programme.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef _INPUT_BUFFER_HH_
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#define _INPUT_BUFFER_HH_
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#include "util.hh"
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#include <assert.h>
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namespace dtc
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{
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/**
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* Class encapsulating the input file. Can be used as a const char*, but has
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* range checking. Attempting to access anything out of range will return a 0
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* byte. The input buffer can be cheaply copied, without copying the
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* underlying memory, however it is the user's responsibility to ensure that
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* such copies do not persist beyond the lifetime of the underlying memory.
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*
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* This also contains methods for reporting errors and for consuming the token
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* stream.
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*/
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class input_buffer
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{
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protected:
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/**
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* The buffer. This class doesn't own the buffer, but the
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* mmap_input_buffer subclass does.
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*/
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const char* buffer;
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/**
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* The size of the buffer.
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*/
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int size;
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private:
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/**
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* The current place in the buffer where we are reading. This class
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* keeps a separate size, pointer, and cursor so that we can move
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* forwards and backwards and still have checks that we haven't fallen
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* off either end.
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*/
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int cursor;
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/**
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* Private constructor. This is used to create input buffers that
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* refer to the same memory, but have different cursors.
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*/
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input_buffer(const char* b, int s, int c) : buffer(b), size(s),
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cursor(c) {}
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/**
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* Reads forward past any spaces. The DTS format is not whitespace
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* sensitive and so we want to scan past whitespace when reading it.
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*/
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void skip_spaces();
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public:
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/**
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* Virtual destructor. Does nothing, but exists so that subclasses
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* that own the memory can run cleanup code for deallocating it.
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*/
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virtual ~input_buffer() {};
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/**
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* Constructs an empty buffer.
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*/
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input_buffer() : buffer(0), size(0), cursor(0) {}
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/**
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* Constructs a new buffer with a specified memory region and size.
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*/
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input_buffer(const char* b, int s) : buffer(b), size(s), cursor(0){}
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/**
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* Returns a new input buffer referring into this input, clamped to the
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* specified size. If the requested buffer would fall outside the
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* range of this one, then it returns an empty buffer.
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*
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* The returned buffer shares the same underlying storage as the
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* original. This is intended to be used for splitting up the various
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* sections of a device tree blob. Requesting a size of 0 will give a
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* buffer that extends to the end of the available memory.
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*/
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input_buffer buffer_from_offset(int offset, int s=0);
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/**
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* Returns true if this buffer has no unconsumed space in it.
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*/
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inline bool empty()
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{
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return cursor >= size;
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}
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/**
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* Dereferencing operator, allows the buffer to be treated as a char*
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* and dereferenced to give a character. This returns a null byte if
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* the cursor is out of range.
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*/
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inline char operator*()
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{
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if (cursor >= size) { return '\0'; }
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if (cursor < 0) { return '\0'; }
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return buffer[cursor];
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}
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/**
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* Array subscripting operator, returns a character at the specified
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* index offset from the current cursor. The offset may be negative,
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* to reread characters that have already been read. If the current
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* cursor plus offset is outside of the range, this returns a nul
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* byte.
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*/
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inline char operator[](int offset)
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{
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if (cursor + offset >= size) { return '\0'; }
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if (cursor + offset < 0) { return '\0'; }
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return buffer[cursor + offset];
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}
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/**
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* Increments the cursor, iterating forward in the buffer.
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*/
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inline input_buffer &operator++()
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{
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cursor++;
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return *this;
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}
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/**
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* Cast to char* operator. Returns a pointer into the buffer that can
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* be used for constructing strings.
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*/
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inline operator const char*()
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{
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if (cursor >= size) { return 0; }
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if (cursor < 0) { return 0; }
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return &buffer[cursor];
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}
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/**
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* Consumes a character. Moves the cursor one character forward if the
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* next character matches the argument, returning true. If the current
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* character does not match the argument, returns false.
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*/
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inline bool consume(char c)
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{
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if ((*this)[0] == c)
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{
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++(*this);
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return true;
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}
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return false;
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}
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/**
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* Consumes a string. If the (null-terminated) string passed as the
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* argument appears in the input, advances the cursor to the end and
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* returns true. Returns false if the string does not appear at the
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* current point in the input.
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*/
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bool consume(const char *str);
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/**
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* Reads an integer in base 8, 10, or 16. Returns true and advances
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* the cursor to the end of the integer if the cursor points to an
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* integer, returns false and does not move the cursor otherwise.
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*
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* The parsed value is returned via the argument.
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*/
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bool consume_integer(long long &outInt);
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/**
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* Template function that consumes a binary value in big-endian format
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* from the input stream. Returns true and advances the cursor if
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* there is a value of the correct size. This function assumes that
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* all values must be natively aligned, and so advances the cursor to
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* the correct alignment before reading.
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*/
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template<typename T>
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bool consume_binary(T &out)
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{
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int align = 0;
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int type_size = sizeof(T);
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if (cursor % type_size != 0)
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{
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align = type_size - (cursor % type_size);
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}
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if (size < cursor + align + type_size)
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{
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return false;
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}
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cursor += align;
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assert(cursor % type_size == 0);
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out = 0;
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for (int i=0 ; i<type_size ; ++i)
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{
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out <<= 8;
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out |= (((T)buffer[cursor++]) & 0xff);
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}
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return true;
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}
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/**
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* Consumes two hex digits and return the resulting byte via the first
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* argument. If the next two characters are hex digits, returns true
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* and advances the cursor. If not, then returns false and leaves the
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* cursor in place.
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*/
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bool consume_hex_byte(uint8_t &outByte);
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/**
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* Advances the cursor to the start of the next token, skipping
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* comments and whitespace. If the cursor already points to the start
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* of a token, then this function does nothing.
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*/
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input_buffer &next_token();
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/**
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* Prints a message indicating the location of a parse error.
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*/
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void parse_error(const char *msg);
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/**
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* Dumps the current cursor value and the unconsumed values in the
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* input buffer to the standard error. This method is intended solely
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* for debugging.
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*/
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void dump();
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};
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/**
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* Explicit specialisation for reading a single byte.
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*/
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template<>
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inline bool input_buffer::consume_binary(uint8_t &out)
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{
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if (size < cursor + 1)
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{
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return false;
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}
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out = buffer[cursor++];
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return true;
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}
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/**
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* Subclass of input_buffer that mmap()s a file and owns the resulting memory.
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* When this object is destroyed, the memory is unmapped.
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*/
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struct mmap_input_buffer : public input_buffer
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{
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/**
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* Constructs a new buffer from the file passed in as a file
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* descriptor.
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*/
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mmap_input_buffer(int fd);
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/**
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* Unmaps the buffer, if one exists.
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*/
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virtual ~mmap_input_buffer();
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};
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/**
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* Input buffer read from standard input. This is used for reading device tree
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* blobs and source from standard input. It reads the entire input into
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* malloc'd memory, so will be very slow for large inputs. DTS and DTB files
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* are very rarely more than 10KB though, so this is probably not a problem.
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*/
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struct stream_input_buffer : public input_buffer
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{
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/**
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* The buffer that will store the data read from the standard input.
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*/
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std::vector<char> b;
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/**
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* Constructs a new buffer from the standard input.
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*/
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stream_input_buffer();
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};
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} // namespace dtc
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#endif // !_INPUT_BUFFER_HH_
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