4cpp Lexing Library

Cpp_Get_Token_Result cpp_get_token()

A Cpp_Get_Token_Result struct is returned containing the index of a token and a flag indicating whether the pos is contained in the token or in whitespace after the token.

This call performs a binary search over all of the tokens looking for the token that contains the specified position. If the position is in whitespace between the tokens, the returned token index is the index of the token immediately before the provided position. The returned index can be -1 if the position is before the first token.

Cpp_Lex_Result cpp_lex_step()

This call is the primary interface of the lexing system. It is quite general so it can be used in a lot of different ways. I will explain the general rules first, and then give some examples of common ways it might be used.

First a lexing state, Cpp_Lex_Data, must be initialized. The file to lex must be read into N contiguous chunks of memory. An output Cpp_Token_Array must be allocated and initialized with the appropriate count and max_count values. Then each chunk of the file must be passed to cpp_lex_step in order using the same lexing state for each call. Every time a call to cpp_lex_step returns LexResult_NeedChunk, the next call to cpp_lex_step should use the next chunk. If the return is some other value, the lexer hasn't finished with the current chunk and it sopped for some other reason, so the same chunk should be used again in the next call.

If the file chunks contain a null terminator the lexer will return LexResult_Finished when it finds this character. At this point calling the lexer again with the same state will result in an error. If you do not have a null terminated chunk to end the file, you may instead pass the exact size in bytes of the entire file to the full_size parameter and it will automatically handle the termination of the lexing state when it has read that many bytes. If a full_size is specified and the system terminates for having seen that many bytes, it will return LexResult_Finished. If a full_size is specified and a null character is read before the total number of bytes have been read the system will still terminate as usual and return LexResult_Finished.

If the system has filled the entire output array it will return LexResult_NeedTokenMemory. When this happens if you want to continue lexing the file you can grow the token array, or switch to a new output array and then call cpp_lex_step again with the chunk that was being lexed and the new output. You can also specify a max_tokens_out which is limits how many new tokens will be added to the token array. Even if token_array_out still had more space to hold tokens, if the max_tokens_out limit is hit, the lexer will stop and return LexResult_HitTokenLimit. If this happens there is still space left in the token array, so you can resume simply by calling cpp_lex_step again with the same chunk and the same output array. Also note that, unlike the chunks which must only be replaced when the system says it needs a chunk. You may switch to or modify the output array in between calls as much as you like.

The most basic use of this system is to get it all done in one big chunk and try to allocate a nearly "infinite" output array so that it will not run out of memory. This way you can get the entire job done in one call and then just assert to make sure it returns LexResult_Finished to you:

Cpp_Lex_Data cpp_lex_data_init()

A brand new lex state ready to begin lexing a file from the beginning.

Creates a new lex state in the form of a Cpp_Lex_Data struct and returns the struct. The system needs a temporary buffer that is as long as the longest token. 4096 is usually enough but the buffer is not checked, so to be 100% bullet proof it has to be the same length as the file being lexed.

int32_t cpp_lex_data_temp_size()

This call gets the current size of the temporary buffer in the lexer state so that you can move to a new temporary buffer by copying the data over.

void cpp_lex_data_temp_read()

This call reads the current contents of the temporary buffer.

void cpp_lex_data_new_temp()

This call can be used to set a new temporary buffer for the lex state. In cases where you want to discontinue lexing, store the state, and resume later. In such a situation it may be necessary for you to free the temp buffer that was originally used to make the lex state. This call allows you to supply a new temp buffer when you are ready to resume lexing.

However the new buffer needs to have the same contents the old buffer had. To ensure this you have to use cpp_lex_data_temp_size and cpp_lex_data_temp_read to get the relevant contents of the temp buffer before you free it.

Cpp_Token_Array cpp_make_token_array()

An empty Cpp_Token_Array with memory malloc'd for storing tokens.

This call allocates a Cpp_Token_Array with malloc for use in other convenience functions. Stacks that are not allocated this way should not be used in the convenience functions.

void cpp_free_token_array()

This call frees a Cpp_Token_Array.

void cpp_resize_token_array()

This call allocates a new memory chunk and moves the existing tokens in the array over to the new chunk.

void cpp_lex_file()

Lexes an entire file and manages the interaction with the lexer system so that it is quick and convenient to lex files.

enum Cpp_Token_Type;

A Cpp_Token_Type classifies a token to make parsing easier. Some types are not actually output by the lexer, but exist because parsers will also make use of token types in their own output.

struct Cpp_Token {
};

Cpp_Token represents a single lexed token. It is the primary output of the lexing system.

enum Cpp_Token_Flag;

The Cpp_Token_Flags are used to mark up tokens with additional information.

struct Cpp_Token_Array {
};

Cpp_Token_Array is used to bundle together the common elements of a growing array of Cpp_Tokens. To initialize it the tokens field should point to a block of memory with a size equal to max_count*sizeof(Cpp_Token) and the count should be initialized to zero.

struct Cpp_Get_Token_Result {
};

Cpp_Get_Token_Result is the return result of the cpp_get_token call.

struct Cpp_Lex_Data { /* non-public internals */ } ;

Cpp_Lex_Data represents the state of the lexer so that the system may be resumable and the user can manage the lexer state and decide when to resume lexing with it. To create a new lexer state that has not begun doing any lexing work call cpp_lex_data_init.

The internals of the lex state should not be treated as a part of the public API.

enum Cpp_Lex_Result;

Cpp_Lex_Result is returned from the lexing engine to indicate why it stopped lexing.