253 lines
9.7 KiB
C
253 lines
9.7 KiB
C
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/**
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* @file in.h
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* @author Radek Krejci <rkrejci@cesnet.cz>
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* @brief libyang input structures and functions
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*
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* Copyright (c) 2020 CESNET, z.s.p.o.
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*
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* This source code is licensed under BSD 3-Clause License (the "License").
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* You may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://opensource.org/licenses/BSD-3-Clause
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*/
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#ifndef LY_IN_H_
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#define LY_IN_H_
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#include <stdio.h>
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#include "log.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @page howtoInput Input Processing
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*
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* libyang provides a mechanism to generalize work with the inputs (and [outputs](@ref howtoOutput)) of
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* the different types. The ::ly_in handler can be created providing necessary information connected with the specific
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* input type and then used throughout the parser functions processing the input data. Using a generic input handler avoids
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* need to have a set of functions for each parser functionality and results in simpler API.
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*
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* The API allows to alter the source of the data behind the handler by another source. Also resetting a seekable source
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* input is possible with ::ly_in_reset() to re-read the input.
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*
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* @note
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* Currently, libyang supports only reading data from standard (disk) file, not from sockets, pipes, etc. The reason is
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* that the parsers expects all the data to be present in the file (input data are complete). In future, we would like
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* to change the internal mechanism and support sequential processing of the input data. In XML wording - we have DOM
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* parser, but in future we would like to move to something like a SAX parser.
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*
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* @note
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* This mechanism was introduced in libyang 2.0. To simplify transition from libyang 1.0 to version 2.0 and also for
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* some simple use case where using the input handler would be an overkill, there are some basic parsers functions
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* that do not require input handler. But remember, that functionality of these function can be limited in particular cases
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* in contrast to the functions using input handlers.
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*
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* Functions List
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* --------------
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* - ::ly_in_new_fd()
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* - ::ly_in_new_file()
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* - ::ly_in_new_filepath()
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* - ::ly_in_new_memory()
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*
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* - ::ly_in_fd()
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* - ::ly_in_file()
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* - ::ly_in_filepath()
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* - ::ly_in_memory()
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*
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* - ::ly_in_type()
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* - ::ly_in_parsed()
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*
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* - ::ly_in_reset()
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* - ::ly_in_free()
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*
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* libyang Parsers List
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* --------------------
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* - @subpage howtoSchemaParsers
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* - @subpage howtoDataParsers
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*/
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/**
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* @struct ly_in
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* @brief Parser input structure specifying where the data are read.
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*/
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struct ly_in;
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/**
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* @brief Types of the parser's inputs
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*/
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typedef enum LY_IN_TYPE {
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LY_IN_ERROR = -1, /**< error value to indicate failure of the functions returning LY_IN_TYPE */
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LY_IN_FD, /**< file descriptor printer */
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LY_IN_FILE, /**< FILE stream parser */
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LY_IN_FILEPATH, /**< filepath parser */
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LY_IN_MEMORY /**< memory parser */
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} LY_IN_TYPE;
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/**
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* @brief Get input type of the input handler.
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*
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* @param[in] in Input handler.
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* @return Type of the parser's input.
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*/
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LIBYANG_API_DECL LY_IN_TYPE ly_in_type(const struct ly_in *in);
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/**
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* @brief Reset the input medium to read from its beginning, so the following parser function will read from the object's beginning.
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*
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* Note that in case the underlying output is not seekable (stream referring a pipe/FIFO/socket or the callback output type),
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* nothing actually happens despite the function succeeds. Also note that the medium is not returned to the state it was when
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* the handler was created. For example, file is seeked into the offset zero, not to the offset where it was opened when
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* ::ly_in_new_file() was called.
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*
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* @param[in] in Input handler.
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* @return LY_SUCCESS in case of success
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* @return LY_ESYS in case of failure
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*/
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LIBYANG_API_DECL LY_ERR ly_in_reset(struct ly_in *in);
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/**
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* @brief Create input handler using file descriptor.
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*
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* @param[in] fd File descriptor to use.
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* @param[out] in Created input handler supposed to be passed to different ly*_parse() functions.
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* @return LY_SUCCESS in case of success
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* @return LY_ERR value in case of failure.
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*/
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LIBYANG_API_DECL LY_ERR ly_in_new_fd(int fd, struct ly_in **in);
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/**
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* @brief Get or reset file descriptor input handler.
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*
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* @param[in] in Input handler.
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* @param[in] fd Optional value of a new file descriptor for the handler. If -1, only the current file descriptor value is returned.
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* @return Previous value of the file descriptor. Note that caller is responsible for closing the returned file descriptor in case of setting new descriptor @p fd.
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* @return -1 in case of error when setting up the new file descriptor.
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*/
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LIBYANG_API_DECL int ly_in_fd(struct ly_in *in, int fd);
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/**
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* @brief Create input handler using file stream.
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*
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* @param[in] f File stream to use.
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* @param[out] in Created input handler supposed to be passed to different ly*_parse() functions.
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* @return LY_SUCCESS in case of success
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* @return LY_ERR value in case of failure.
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*/
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LIBYANG_API_DECL LY_ERR ly_in_new_file(FILE *f, struct ly_in **in);
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/**
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* @brief Get or reset file stream input handler.
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*
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* @param[in] in Input handler.
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* @param[in] f Optional new file stream for the handler. If NULL, only the current file stream is returned.
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* @return NULL in case of invalid argument or an error when setting up the new input file, original input handler @p in is untouched in this case.
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* @return Previous file stream of the handler. Note that caller is responsible for closing the returned stream in case of setting new stream @p f.
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*/
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LIBYANG_API_DECL FILE *ly_in_file(struct ly_in *in, FILE *f);
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/**
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* @brief Create input handler using memory to read data.
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*
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* @param[in] str Pointer where to start reading data. The input data are expected to be NULL-terminated.
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* Note that in case the destroy argument of ::ly_in_free() is used, the input string is passed to free(),
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* so if it is really a static string, do not use the destroy argument!
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* @param[out] in Created input handler supposed to be passed to different ly*_parse() functions.
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* @return LY_SUCCESS in case of success
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* @return LY_ERR value in case of failure.
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*/
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LIBYANG_API_DECL LY_ERR ly_in_new_memory(const char *str, struct ly_in **in);
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/**
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* @brief Get or change memory where the data are read from.
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*
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* @param[in] in Input handler.
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* @param[in] str String containing the data to read. The input data are expected to be NULL-terminated.
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* Note that in case the destroy argument of ::ly_in_free() is used, the input string is passed to free(),
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* so if it is really a static string, do not use the destroy argument!
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* @return Previous starting address to read data from. Note that the caller is responsible to free
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* the data in case of changing string pointer @p str.
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*/
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LIBYANG_API_DECL const char *ly_in_memory(struct ly_in *in, const char *str);
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/**
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* @brief Create input handler file of the given filename.
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*
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* @param[in] filepath Path of the file where to read data.
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* @param[in] len Optional number of bytes to use from @p filepath. If 0, the @p filepath is considered to be NULL-terminated and
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* the whole string is taken into account.
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* @param[out] in Created input handler supposed to be passed to different ly*_parse() functions.
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* @return LY_SUCCESS in case of success
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* @return LY_ERR value in case of failure.
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*/
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LIBYANG_API_DECL LY_ERR ly_in_new_filepath(const char *filepath, size_t len, struct ly_in **in);
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/**
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* @brief Get or change the filepath of the file where the parser reads the data.
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*
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* Note that in case of changing the filepath, the current file is closed and a new one is
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* created/opened instead of renaming the previous file. Also note that the previous filepath
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* string is returned only in case of not changing it's value.
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*
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* @param[in] in Input handler.
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* @param[in] filepath Optional new filepath for the handler. If and only if NULL, the current filepath string is returned.
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* @param[in] len Optional number of bytes to use from @p filepath. If 0, the @p filepath is considered to be NULL-terminated and
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* the whole string is taken into account.
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* @return Previous filepath string in case the @p filepath argument is NULL.
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* @return NULL if changing filepath succeedes and ((void *)-1) otherwise.
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*/
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LIBYANG_API_DECL const char *ly_in_filepath(struct ly_in *in, const char *filepath, size_t len);
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/**
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* @brief Get the number of parsed bytes by the last function.
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*
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* @param[in] in In structure used.
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* @return Number of parsed bytes.
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*/
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LIBYANG_API_DECL size_t ly_in_parsed(const struct ly_in *in);
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/**
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* @brief Free the input handler.
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*
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* @param[in] in Input handler to free.
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* @param[in] destroy Flag to free the input data buffer (for LY_IN_MEMORY) or to
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* close stream/file descriptor (for LY_IN_FD and LY_IN_FILE)
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*/
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LIBYANG_API_DECL void ly_in_free(struct ly_in *in, ly_bool destroy);
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/**
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* @brief Read bytes from an input.
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*
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* Does not count new lines, which is expected from the caller who has better idea about
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* the content of the read data and can better optimize counting.
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*
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* @param[in] in Input structure.
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* @param[in] buf Destination buffer.
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* @param[in] count Number of bytes to read.
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* @return LY_SUCCESS on success,
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* @return LY_EDENIED on EOF.
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*/
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LIBYANG_API_DECL LY_ERR ly_in_read(struct ly_in *in, void *buf, size_t count);
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/**
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* @brief Just skip bytes in an input.
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*
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* Does not count new lines, which is expected from the caller who has better idea about
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* the content of the skipped data and can better optimize counting.
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*
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* @param[in] in Input structure.
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* @param[in] count Number of bytes to skip.
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* @return LY_SUCCESS on success,
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* @return LY_EDENIED on EOF.
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*/
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LIBYANG_API_DECL LY_ERR ly_in_skip(struct ly_in *in, size_t count);
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#ifdef __cplusplus
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}
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#endif
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#endif /* LY_IN_H_ */
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