git/Documentation/technical/api-argv-array.txt
Jeff King c1189caeaf refactor argv_array into generic code
The submodule code recently grew generic code to build a
dynamic argv array. Many other parts of the code can reuse
this, too, so let's make it generically available.

There are two enhancements not found in the original code:

  1. We now handle the NULL-termination invariant properly,
     even when no strings have been pushed (before, you
     could have an empty, NULL argv). This was not a problem
     for the submodule code, which always pushed at least
     one argument, but was not sufficiently safe for
     generic code.

  2. There is a formatted variant of the "push" function.
     This is a convenience function which was not needed by
     the submodule code, but will make it easier to port
     other users to the new code.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-09-14 11:56:36 -07:00

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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_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_clear`::
Free all memory associated with the array and return it to the
initial, empty state.