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git/Documentation/technical/api-argv-array.txt
Jeff King b992657ed0 argv-array: add detach function
The usual pattern for an argv array is to initialize it,
push in some strings, and then clear it when done. Very
occasionally, though, we must do other exotic things with
the memory, like freeing the list but keeping the strings.
Let's provide a detach function so that callers can make use
of our API to build up the array, and then take ownership of
it.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-02-22 14:50:32 -08:00

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argv-array API
==============
The argv-array API allows one to dynamically build and store
NULL-terminated lists. An argv-array maintains the invariant that the
`argv` member always points to a non-NULL array, and that the array is
always NULL-terminated at the element pointed to by `argv[argc]`. This
makes the result suitable for passing to functions expecting to receive
argv from main(), or the link:api-run-command.html[run-command API].
The link:api-string-list.html[string-list API] is similar, but cannot be
used for these purposes; instead of storing a straight string pointer,
it contains an item structure with a `util` field that is not compatible
with the traditional argv interface.
Each `argv_array` manages its own memory. Any strings pushed into the
array are duplicated, and all memory is freed by argv_array_clear().
Data Structures
---------------
`struct argv_array`::
A single array. This should be initialized by assignment from
`ARGV_ARRAY_INIT`, or by calling `argv_array_init`. The `argv`
member contains the actual array; the `argc` member contains the
number of elements in the array, not including the terminating
NULL.
Functions
---------
`argv_array_init`::
Initialize an array. This is no different than assigning from
`ARGV_ARRAY_INIT`.
`argv_array_push`::
Push a copy of a string onto the end of the array.
`argv_array_pushl`::
Push a list of strings onto the end of the array. The arguments
should be a list of `const char *` strings, terminated by a NULL
argument.
`argv_array_pushf`::
Format a string and push it onto the end of the array. This is a
convenience wrapper combining `strbuf_addf` and `argv_array_push`.
`argv_array_pushv`::
Push a null-terminated array of strings onto the end of the array.
`argv_array_pop`::
Remove the final element from the array. If there are no
elements in the array, do nothing.
`argv_array_clear`::
Free all memory associated with the array and return it to the
initial, empty state.
`argv_array_detach`::
Disconnect the `argv` member from the `argv_array` struct and
return it. The caller is responsible for freeing the memory used
by the array, and by the strings it references. After detaching,
the `argv_array` is in a reinitialized state and can be pushed
into again.