Table and Array Functions

Overview

Arrays are used to store data which is referenced sequentially or as a stack. More…

// typedefs

typedef struct apr_table_t apr_table_t;
typedef struct apr_array_header_t apr_array_header_t;
typedef struct apr_table_entry_t apr_table_entry_t;

typedef int() apr_table_do_callback_fn_t(
    void *rec,
    const char *key,
    const char *value
    );

// structs

struct apr_array_header_t;
struct apr_table_entry_t;

// global functions

const apr_array_header_t*
apr_table_elts(const apr_table_t* t);

int
apr_is_empty_table(const apr_table_t* t);

int
apr_is_empty_array(const apr_array_header_t* a);

apr_array_header_t*
apr_array_make(
    apr_pool_t* p,
    int nelts,
    int elt_size
);

void*
apr_array_push(apr_array_header_t* arr);

void*
apr_array_pop(apr_array_header_t* arr);

void
apr_array_clear(apr_array_header_t* arr);

void
apr_array_cat(
    apr_array_header_t* dst,
    const apr_array_header_t* src
);

apr_array_header_t*
apr_array_copy(
    apr_pool_t* p,
    const apr_array_header_t* arr
);

apr_array_header_t*
apr_array_copy_hdr(
    apr_pool_t* p,
    const apr_array_header_t* arr
);

apr_array_header_t*
apr_array_append(
    apr_pool_t* p,
    const apr_array_header_t* first,
    const apr_array_header_t* second
);

char*
apr_array_pstrcat(
    apr_pool_t* p,
    const apr_array_header_t* arr,
    const char sep
);

apr_table_t*
apr_table_make(
    apr_pool_t* p,
    int nelts
);

apr_table_t*
apr_table_copy(
    apr_pool_t* p,
    const apr_table_t* t
);

apr_table_t*
apr_table_clone(
    apr_pool_t* p,
    const apr_table_t* t
);

void
apr_table_clear(apr_table_t* t);

const char*
apr_table_get(
    const apr_table_t* t,
    const char* key
);

const char*
apr_table_getm(
    apr_pool_t* p,
    const apr_table_t* t,
    const char* key
);

void
apr_table_set(
    apr_table_t* t,
    const char* key,
    const char* val
);

void
apr_table_setn(
    apr_table_t* t,
    const char* key,
    const char* val
);

void
apr_table_unset(
    apr_table_t* t,
    const char* key
);

void
apr_table_merge(
    apr_table_t* t,
    const char* key,
    const char* val
);

void
apr_table_mergen(
    apr_table_t* t,
    const char* key,
    const char* val
);

void
apr_table_add(
    apr_table_t* t,
    const char* key,
    const char* val
);

void
apr_table_addn(
    apr_table_t* t,
    const char* key,
    const char* val
);

apr_table_t*
apr_table_overlay(
    apr_pool_t* p,
    const apr_table_t* overlay,
    const apr_table_t* base
);

int
apr_table_do(
    apr_table_do_callback_fn_t* comp,
    void* rec,
    const apr_table_t* t,
    ...
);

int
apr_table_vdo(
    apr_table_do_callback_fn_t* comp,
    void* rec,
    const apr_table_t* t,
    va_list vp
);

void
apr_table_overlap(
    apr_table_t* a,
    const apr_table_t* b,
    unsigned flags
);

void
apr_table_compress(
    apr_table_t* t,
    unsigned flags
);

// macros

#define APR_ARRAY_IDX( \
    ary, \
    i, \
    type \
)

#define APR_ARRAY_PUSH( \
    ary, \
    type \
)

#define APR_OVERLAP_TABLES_MERGE
#define APR_OVERLAP_TABLES_SET

Detailed Documentation

Arrays are used to store data which is referenced sequentially or as a stack. Functions are provided to push and pop individual elements as well as to operate on the entire array.

Tables are used to store data which can be referenced by key. Limited capabilities are provided for tables with multiple elements which share a key; while key lookup will return only a single element, iteration is available. Additionally, a table can be compressed to resolve duplicates.

Both arrays and tables may store string or binary data; some features, such as concatenation or merging of elements, work only for string data.

Typedefs

typedef struct apr_table_t apr_table_t

the table abstract data type

typedef struct apr_array_header_t apr_array_header_t

See also:

apr_array_header_t

typedef struct apr_table_entry_t apr_table_entry_t

The (opaque) structure for string-content tables.

typedef int() apr_table_do_callback_fn_t(
    void *rec,
    const char *key,
    const char *value
    )

Declaration prototype for the iterator callback function of apr_table_do() and apr_table_vdo(). Iteration continues while this callback function returns non-zero. To export the callback function for apr_table_[v]do() it must be declared in the _NONSTD convention.

Parameters:

rec	The data passed as the first argument to apr_table_[v]do()
key	The key from this iteration of the table
value	The value from this iteration of the table

Global Functions

const apr_array_header_t*
apr_table_elts(const apr_table_t* t)

Get the elements from a table.

Parameters:

t

The table

Returns:

An array containing the contents of the table

int
apr_is_empty_table(const apr_table_t* t)

Determine if the table is empty (either NULL or having no elements).

Parameters:

t	The table to check

Returns:

True if empty, False otherwise

int
apr_is_empty_array(const apr_array_header_t* a)

Determine if the array is empty (either NULL or having no elements).

Parameters:

a	The array to check

Returns:

True if empty, False otherwise

apr_array_header_t*
apr_array_make(
    apr_pool_t* p,
    int nelts,
    int elt_size
)

Create an array.

Parameters:

p	The pool to allocate the memory out of
nelts	the number of elements in the initial array
elt_size	The size of each element in the array.

Returns:

The new array

void*
apr_array_push(apr_array_header_t* arr)

Add a new element to an array (as a first-in, last-out stack). If there are no free spots in the array, then this function will allocate new space for the new element.

Parameters:

arr	The array to add an element to.

Returns:

Location for the new element in the array.

void*
apr_array_pop(apr_array_header_t* arr)

Remove an element from an array (as a first-in, last-out stack). If there are no elements in the array, NULL is returned.

Parameters:

arr	The array to remove an element from.

Returns:

Location of the element in the array.

void
apr_array_clear(apr_array_header_t* arr)

Remove all elements from an array. As the underlying storage is allocated from a pool, no memory is freed by this operation, but is available for reuse.

Parameters:

arr	The array to remove all elements from.

void
apr_array_cat(
    apr_array_header_t* dst,
    const apr_array_header_t* src
)

Concatenate two arrays together.

Parameters:

dst	The destination array, and the one to go first in the combined array
src	The source array to add to the destination array

apr_array_header_t*
apr_array_copy(
    apr_pool_t* p,
    const apr_array_header_t* arr
)

Copy the entire array. The alternate apr_array_copy_hdr copies only the header, and arranges for the elements to be copied if (and only if) the code subsequently does a push or arraycat.

Parameters:

p	The pool to allocate the copy of the array out of
arr	The array to copy

Returns:

An exact copy of the array passed in

apr_array_header_t*
apr_array_copy_hdr(
    apr_pool_t* p,
    const apr_array_header_t* arr
)

Copy the headers of the array, and arrange for the elements to be copied if and only if the code subsequently does a push or arraycat. The alternate apr_array_copy copies the entire array.

Parameters:

p	The pool to allocate the copy of the array out of
arr	The array to copy

Returns:

An exact copy of the array passed in

apr_array_header_t*
apr_array_append(
    apr_pool_t* p,
    const apr_array_header_t* first,
    const apr_array_header_t* second
)

Append one array to the end of another, creating a new array in the process.

Parameters:

p	The pool to allocate the new array out of
first	The array to put first in the new array.
second	The array to put second in the new array.

Returns:

A new array containing the data from the two arrays passed in.

char*
apr_array_pstrcat(
    apr_pool_t* p,
    const apr_array_header_t* arr,
    const char sep
)

Generate a new string from the apr_pool_t containing the concatenated sequence of substrings referenced as elements within the array. The string will be empty if all substrings are empty or null, or if there are no elements in the array. If sep is non-NUL, it will be inserted between elements as a separator.

Parameters:

p	The pool to allocate the string out of
arr	The array to generate the string from
sep	The separator to use

Returns:

A string containing all of the data in the array.

apr_table_t*
apr_table_make(
    apr_pool_t* p,
    int nelts
)

Make a new table.

Warning

This table can only store text data

Parameters:

p	The pool to allocate the pool out of
nelts	The number of elements in the initial table.

Returns:

The new table.

apr_table_t*
apr_table_copy(
    apr_pool_t* p,
    const apr_table_t* t
)

Create a new table and copy another table into it.

Warning

The table keys and respective values are not copied

Parameters:

p	The pool to allocate the new table out of
t	The table to copy

Returns:

A copy of the table passed in

apr_table_t*
apr_table_clone(
    apr_pool_t* p,
    const apr_table_t* t
)

Create a new table whose contents are deep copied from the given table. A deep copy operation copies all fields, and makes copies of dynamically allocated memory pointed to by the fields.

Parameters:

p	The pool to allocate the new table out of
t	The table to clone

Returns:

A deep copy of the table passed in

void
apr_table_clear(apr_table_t* t)

Delete all of the elements from a table.

Parameters:

t	The table to clear

const char*
apr_table_get(
    const apr_table_t* t,
    const char* key
)

Get the value associated with a given key from the table. After this call, the data is still in the table.

Parameters:

t	The table to search for the key
key	The key to search for (case does not matter)

Returns:

The value associated with the key, or NULL if the key does not exist.

const char*
apr_table_getm(
    apr_pool_t* p,
    const apr_table_t* t,
    const char* key
)

Get values associated with a given key from the table. If more than one value exists, return a comma separated list of values. After this call, the data is still in the table.

Parameters:

p	The pool to allocate the combined value from, if necessary
t	The table to search for the key
key	The key to search for (case does not matter)

Returns:

The value associated with the key, or NULL if the key does not exist.

void
apr_table_set(
    apr_table_t* t,
    const char* key,
    const char* val
)

Add a key/value pair to a table. If another element already exists with the same key, this will overwrite the old data. When adding data, this function makes a copy of both the key and the value.

Parameters:

t	The table to add the data to.
key	The key to use (case does not matter)
val	The value to add

void
apr_table_setn(
    apr_table_t* t,
    const char* key,
    const char* val
)

Add a key/value pair to a table. If another element already exists with the same key, this will overwrite the old data.

Warning

When adding data, this function does not make a copy of the key or the value, so care should be taken to ensure that the values will not change after they have been added..

Parameters:

t	The table to add the data to.
key	The key to use (case does not matter)
val	The value to add

void
apr_table_unset(
    apr_table_t* t,
    const char* key
)

Remove data from the table.

Parameters:

t	The table to remove data from
key	The key of the data being removed (case does not matter)

void
apr_table_merge(
    apr_table_t* t,
    const char* key,
    const char* val
)

Add data to a table by merging the value with data that has already been stored. The merging is done by concatenating the two values, separated by the string “, “. If the key is not found, then this function acts like apr_table_add

Parameters:

t	The table to search for the data
key	The key to merge data for (case does not matter)
val	The data to add

void
apr_table_mergen(
    apr_table_t* t,
    const char* key,
    const char* val
)

Add data to a table by merging the value with data that has already been stored. The merging is done by concatenating the two values, separated by the string “, “. If the key is not found, then this function acts like apr_table_addn

Parameters:

t	The table to search for the data
key	The key to merge data for (case does not matter)
val	The data to add

void
apr_table_add(
    apr_table_t* t,
    const char* key,
    const char* val
)

Add data to a table, regardless of whether there is another element with the same key. When adding data, this function makes a copy of both the key and the value.

Parameters:

t	The table to add to
key	The key to use
val	The value to add.

void
apr_table_addn(
    apr_table_t* t,
    const char* key,
    const char* val
)

Add data to a table, regardless of whether there is another element with the same key. When adding data, this function does not make a copy of the key or the value, so care should be taken to ensure that the values will not change after they have been added.

Parameters:

t	The table to add to
key	The key to use
val	The value to add.

apr_table_t*
apr_table_overlay(
    apr_pool_t* p,
    const apr_table_t* overlay,
    const apr_table_t* base
)

Merge two tables into one new table.

Parameters:

p	The pool to use for the new table
overlay	The first table to put in the new table
base	The table to add at the end of the new table

Returns:

A new table containing all of the data from the two passed in

int
apr_table_do(
    apr_table_do_callback_fn_t* comp,
    void* rec,
    const apr_table_t* t,
    ...
)

Iterate over a table running the provided function once for every element in the table. The varargs array must be a list of zero or more (char *) keys followed by a NULL pointer. If zero keys are given, the If an invocation of the

Parameters:

comp	function will be invoked for every element in the table. Otherwise, the function is invoked only for those elements matching the keys specified.
comp	function returns zero, iteration will continue using the next specified key, if any.
comp	The function to run
rec	The data to pass as the first argument to the function
t	The table to iterate over
…	A varargs array of zero or more (char *) keys followed by NULL

Returns:

FALSE if one of the comp() iterations returned zero; TRUE if all iterations returned non-zero

See also:

apr_table_do_callback_fn_t

int
apr_table_vdo(
    apr_table_do_callback_fn_t* comp,
    void* rec,
    const apr_table_t* t,
    va_list vp
)

Iterate over a table running the provided function once for every element in the table. The If an invocation of the

Parameters:

vp	varargs parameter must be a list of zero or more (char *) keys followed by a NULL pointer. If zero keys are given, the
comp	function will be invoked for every element in the table. Otherwise, the function is invoked only for those elements matching the keys specified.
comp	function returns zero, iteration will continue using the next specified key, if any.
comp	The function to run
rec	The data to pass as the first argument to the function
t	The table to iterate over
vp	List of zero or more (char *) keys followed by NULL

Returns:

FALSE if one of the comp() iterations returned zero; TRUE if all iterations returned non-zero

See also:

apr_table_do_callback_fn_t

void
apr_table_overlap(
    apr_table_t* a,
    const apr_table_t* b,
    unsigned flags
)

For each element in table b, either use setn or mergen to add the data to table a. Which method is used is determined by the flags passed in. When merging duplicates, the two values are concatenated, separated by the string “, “.

This function is highly optimized, and uses less memory and CPU cycles than a function that just loops through table b calling other functions. Conceptually, apr_table_overlap does this:

:ref:`apr_array_header_t <doxid-structapr__array__header__t>` *barr = apr_table_elts(b);
:ref:`apr_table_entry_t <doxid-structapr__table__entry__t>` *belt = (:ref:`apr_table_entry_t <doxid-structapr__table__entry__t>` *)barr->elts;
int i;

for (i = 0; i < barr->nelts; ++i) {
    if (flags & APR_OVERLAP_TABLES_MERGE) {
        apr_table_mergen(a, belt[i].key, belt[i].val);
    }
    else {
        apr_table_setn(a, belt[i].key, belt[i].val);
    }
}

Except that it is more efficient (less space and cpu-time) especially when b has many elements.

Notice the assumptions on the keys and values in b they must be in an ancestor of a’s pool. In practice b and a are usually from the same pool.

Parameters:

a	The table to add the data to.
b	The table to iterate over, adding its data to table a
flags	How to add the table to table a. One of: APR_OVERLAP_TABLES_SET Use apr_table_setn APR_OVERLAP_TABLES_MERGE Use apr_table_mergen

void
apr_table_compress(
    apr_table_t* t,
    unsigned flags
)

Eliminate redundant entries in a table by either overwriting or merging duplicates.

When merging duplicates, the two values are concatenated, separated by the string “, “.

Parameters:

t	Table.
flags	APR_OVERLAP_TABLES_MERGE to merge, or APR_OVERLAP_TABLES_SET to overwrite

Macros

#define APR_ARRAY_IDX( \
    ary, \
    i, \
    type \
)

A helper macro for accessing a member of an APR array.

Parameters:

ary	the array
i	the index into the array to return
type	the type of the objects stored in the array

Returns:

the item at index i

#define APR_ARRAY_PUSH( \
    ary, \
    type \
)

A helper macro for pushing elements into an APR array.

Parameters:

ary	the array
type	the type of the objects stored in the array

Returns:

the location where the new object should be placed

#define APR_OVERLAP_TABLES_MERGE

flag for overlap to use apr_table_mergen

#define APR_OVERLAP_TABLES_SET

flag for overlap to use apr_table_setn