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/**
* @file pm_string.h
*
* A generic string type that can have various ownership semantics.
*/
#ifndef PRISM_STRING_H
#define PRISM_STRING_H
#include "prism/defines.h"
#include <assert.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
// The following headers are necessary to read files using demand paging.
#ifdef _WIN32
#include <windows.h>
#elif defined(_POSIX_MAPPED_FILES)
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#endif
/**
* A generic string type that can have various ownership semantics.
*/
typedef struct {
/** A pointer to the start of the string. */
const uint8_t *source;
/** The length of the string in bytes of memory. */
size_t length;
/** The type of the string. This field determines how the string should be freed. */
enum {
/** This string is a constant string, and should not be freed. */
PM_STRING_CONSTANT,
/** This is a slice of another string, and should not be freed. */
PM_STRING_SHARED,
/** This string owns its memory, and should be freed using `pm_string_free`. */
PM_STRING_OWNED,
#ifdef PRISM_HAS_MMAP
/** This string is a memory-mapped file, and should be freed using `pm_string_free`. */
PM_STRING_MAPPED
#endif
} type;
} pm_string_t;
/**
* Returns the size of the pm_string_t struct. This is necessary to allocate the
* correct amount of memory in the FFI backend.
*
* @return The size of the pm_string_t struct.
*/
PRISM_EXPORTED_FUNCTION size_t pm_string_sizeof(void);
/**
* Defines an empty string. This is useful for initializing a string that will
* be filled in later.
*/
#define PM_STRING_EMPTY ((pm_string_t) { .type = PM_STRING_CONSTANT, .source = NULL, .length = 0 })
/**
* Initialize a shared string that is based on initial input.
*
* @param string The string to initialize.
* @param start The start of the string.
* @param end The end of the string.
*/
void pm_string_shared_init(pm_string_t *string, const uint8_t *start, const uint8_t *end);
/**
* Initialize an owned string that is responsible for freeing allocated memory.
*
* @param string The string to initialize.
* @param source The source of the string.
* @param length The length of the string.
*/
void pm_string_owned_init(pm_string_t *string, uint8_t *source, size_t length);
/**
* Initialize a constant string that doesn't own its memory source.
*
* @param string The string to initialize.
* @param source The source of the string.
* @param length The length of the string.
*/
void pm_string_constant_init(pm_string_t *string, const char *source, size_t length);
/**
* Read the file indicated by the filepath parameter into source and load its
* contents and size into the given `pm_string_t`. The given `pm_string_t`
* should be freed using `pm_string_free` when it is no longer used.
*
* We want to use demand paging as much as possible in order to avoid having to
* read the entire file into memory (which could be detrimental to performance
* for large files). This means that if we're on windows we'll use
* `MapViewOfFile`, on POSIX systems that have access to `mmap` we'll use
* `mmap`, and on other POSIX systems we'll use `read`.
*
* @param string The string to initialize.
* @param filepath The filepath to read.
* @return Whether or not the file was successfully mapped.
*/
PRISM_EXPORTED_FUNCTION bool pm_string_mapped_init(pm_string_t *string, const char *filepath);
/**
* Read the file indicated by the filepath parameter into source and load its
* contents and size into the given `pm_string_t`. The given `pm_string_t`
* should be freed using `pm_string_free` when it is no longer used.
*
* @param string The string to initialize.
* @param filepath The filepath to read.
* @return Whether or not the file was successfully read.
*/
PRISM_EXPORTED_FUNCTION bool pm_string_file_init(pm_string_t *string, const char *filepath);
/**
* Ensure the string is owned. If it is not, then reinitialize it as owned and
* copy over the previous source.
*
* @param string The string to ensure is owned.
*/
void pm_string_ensure_owned(pm_string_t *string);
/**
* Compare the underlying lengths and bytes of two strings. Returns 0 if the
* strings are equal, a negative number if the left string is less than the
* right string, and a positive number if the left string is greater than the
* right string.
*
* @param left The left string to compare.
* @param right The right string to compare.
* @return The comparison result.
*/
int pm_string_compare(const pm_string_t *left, const pm_string_t *right);
/**
* Returns the length associated with the string.
*
* @param string The string to get the length of.
* @return The length of the string.
*/
PRISM_EXPORTED_FUNCTION size_t pm_string_length(const pm_string_t *string);
/**
* Returns the start pointer associated with the string.
*
* @param string The string to get the start pointer of.
* @return The start pointer of the string.
*/
PRISM_EXPORTED_FUNCTION const uint8_t * pm_string_source(const pm_string_t *string);
/**
* Free the associated memory of the given string.
*
* @param string The string to free.
*/
PRISM_EXPORTED_FUNCTION void pm_string_free(pm_string_t *string);
#endif
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