freebsd-dev/usr.bin/dtc/input_buffer.hh
David Chisnall c64a3eaf92 Improvements to BSD-licensed DTC.
- Added an expression parser so that expressions from headers are now working
- Fixed missing null terminators on cross references
- Disabled exceptions / RTTI in the build for smaller binaries
- Changed phandle order generation to be identical to GPL'd dtc
2015-12-29 16:29:42 +00:00

317 lines
9.6 KiB
C++

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