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talloc
tree allocator routines
Talloc is a hierarchical memory pool system with destructors: you keep your objects in heirarchies reflecting their lifetime. Every pointer returned from talloc() is itself a valid talloc context, from which other talloc()s can be attached. This means you can do this:
struct foo *X = talloc(mem_ctx, struct foo); X->name = talloc_strdup(X, "foo");
and the pointer X->name would be a "child" of the talloc context "X" which is itself a child of mem_ctx. So if you do talloc_free(mem_ctx) then it is all destroyed, whereas if you do talloc_free(X) then just X and X->name are destroyed, and if you do talloc_free(X->name) then just the name element of X is destroyed.
If you think about this, then what this effectively gives you is an n-ary tree, where you can free any part of the tree with talloc_free().
Talloc has been measured with a time overhead of around 4% over glibc malloc, and 48/80 bytes per allocation (32/64 bit).
This version is based on svn://svnanon.samba.org/samba/branches/SAMBA_4_0/source/lib/talloc revision 23158.
#include <stdio.h>
#include <stdarg.h>
#include <err.h>
#include <ccan/talloc/talloc.h>
// A structure containing a popened command.
struct command
{
FILE *f;
const char *command;
};
// When struct command is freed, we also want to pclose pipe.
static int close_cmd(struct command *cmd)
{
pclose(cmd->f);
// 0 means "we succeeded, continue freeing"
return 0;
}
// This function opens a writable pipe to the given command.
static struct command *open_output_cmd(const void *ctx,
const char *fmt, ...)
{
va_list ap;
struct command *cmd = talloc(ctx, struct command);
if (!cmd)
return NULL;
va_start(ap, fmt);
cmd->command = talloc_vasprintf(cmd, fmt, ap);
va_end(ap);
if (!cmd->command) {
talloc_free(cmd);
return NULL;
}
cmd->f = popen(cmd->command, "w");
if (!cmd->f) {
talloc_free(cmd);
return NULL;
}
talloc_set_destructor(cmd, close_cmd);
return cmd;
}
int main(int argc, char *argv[])
{
struct command *cmd;
if (argc != 2)
errx(1, "Usage: %s <command>\n", argv[0]);
cmd = open_output_cmd(NULL, "%s hello", argv[1]);
if (!cmd)
err(1, "Running '%s hello'", argv[1]);
fprintf(cmd->f, "This is a test\n");
talloc_free(cmd);
return 0;
}
LGPL (v2.1 or any later version)