Add auplugin_setvbuf

The new auplugin_setvbuf functionality allows providing an external
memory buffer and specifies how it should be released through a new
enum auplugin_mem. The state struct now holds both the internal buffer
and a pointer that defaults to it, enabling seamless use of external buffers.

Author: stevegrubb

auplugin/auplugin-fgets.c

@@ -26,7 +26,9 @@
 #include <unistd.h>
 #include <errno.h>
 #include <stdlib.h>
+#include <sys/mman.h>
 #include "libaudit.h"
+#include "auplugin.h"
 
 /*
  * The theory of operation for this family of functions is that it
@@ -44,21 +46,27 @@
 #define BUF_SIZE 8192
 
 struct auplugin_fgets_state {
-	char buffer[2*BUF_SIZE+1];
+	char internal[2*BUF_SIZE+1];
+	char *buffer;
 	char *current;
 	char *eptr;
 	int eof;
+	enum auplugin_mem mem_type;
+	size_t buff_size;
 };
 
 static struct auplugin_fgets_state global_state;
 static int global_init_done;
 
 static void auplugin_fgets_state_init(struct auplugin_fgets_state *st)
 {
-	st->buffer[0] = '\0';
+	st->buffer = st->internal;
+	st->internal[0] = '\0';
 	st->current = st->buffer;
 	st->eptr = st->buffer + (2*BUF_SIZE);
 	st->eof = 0;
+	st->mem_type = MEM_SELF_MANAGED;
+	st->buff_size = 2*BUF_SIZE;
 }
 
 struct auplugin_fgets_state *auplugin_fgets_init(void)
@@ -69,8 +77,22 @@ struct auplugin_fgets_state *auplugin_fgets_init(void)
 	return st;
 }
 
+
 void auplugin_fgets_destroy(struct auplugin_fgets_state *st)
 {
+	if (st->buffer != st->internal) {
+		switch (st->mem_type) {
+		case MEM_MALLOC:
+			free(st->buffer);
+			break;
+		case MEM_MMAP:
+			munmap(st->buffer, st->buff_size);
+			break;
+		case MEM_SELF_MANAGED:
+		default:
+			break;
+		}
+	}
 	free(st);
 }
 
@@ -210,3 +232,20 @@ int auplugin_fgets(char *buf, size_t blen, int fd)
 	return auplugin_fgets_r(&global_state, buf, blen, fd);
 }
 
+void auplugin_setvbuf_r(struct auplugin_fgets_state *st, void *buf,
+			size_t buff_size, enum auplugin_mem how)
+{
+	st->buffer = buf ? buf : st->internal;
+	st->current = st->buffer;
+	st->eptr = st->buffer + buff_size;
+	st->eof = 0;
+	st->mem_type = how;
+	st->buff_size = buff_size;
+}
+
+void auplugin_setvbuf(void *buf, size_t buff_size, enum auplugin_mem how)
+{
+        auplugin_fgets_ensure_global();
+        auplugin_setvbuf_r(&global_state, buf, buff_size, how);
+}
+

auplugin/auplugin.h

@@ -42,11 +42,19 @@ extern "C" {
 
 typedef struct auplugin_fgets_state auplugin_fgets_state_t;
 
+enum auplugin_mem {
+	MEM_MALLOC,
+	MEM_MMAP,
+	MEM_SELF_MANAGED
+};
+
 void auplugin_fgets_clear(void);
 int auplugin_fgets_eof(void);
 int auplugin_fgets_more(size_t blen);
 int auplugin_fgets(char *buf, size_t blen, int fd)
 	__attr_access ((__write_only__, 1, 2));
+void auplugin_setvbuf(void *buf, size_t buff_size, enum auplugin_mem how)
+	__attr_access ((__read_only__, 1, 2));
 
 void auplugin_fgets_destroy(auplugin_fgets_state_t *st);
 auplugin_fgets_state_t *auplugin_fgets_init(void)
@@ -56,6 +64,9 @@ int auplugin_fgets_eof_r(auplugin_fgets_state_t *st);
 int auplugin_fgets_more_r(auplugin_fgets_state_t *st, size_t blen);
 int auplugin_fgets_r(auplugin_fgets_state_t *st, char *buf, size_t blen, int fd)
 	__attr_access ((__write_only__, 2, 3));
+void auplugin_setvbuf_r(auplugin_fgets_state_t *st, void *buf, size_t buff_size,
+			enum auplugin_mem how)
+			__attr_access ((__read_only__, 2, 3));
 
 #ifdef __cplusplus
 }

docs/auplugin_fgets.3

@@ -1,6 +1,6 @@
 .TH "AUPLUGIN_FGETS" "3" "June 2025" "Red Hat" "Linux Audit API"
 .SH NAME
-auplugin_fgets, auplugin_fgets_more, auplugin_fgets_eof, auplugin_fgets_clear \- buffered line reader helpers
+auplugin_fgets, auplugin_fgets_more, auplugin_fgets_eof, auplugin_fgets_clear, auplugin_setvbuf, auplugin_setvbuf_r \- buffered line reader helpers
 .SH SYNOPSIS
 .B #include <auplugin.h>
 .sp
@@ -11,6 +11,10 @@ auplugin_fgets, auplugin_fgets_more, auplugin_fgets_eof, auplugin_fgets_clear \-
 .BI "int auplugin_fgets_eof(void);"
 .br
 .B void auplugin_fgets_clear(void);
+.br
+.BI "void auplugin_setvbuf(void *" buf ", size_t buff_size, enum auplugin_mem " how ");"
+.br
+.BI "void auplugin_setvbuf_r(auplugin_fgets_state_t *" st ", void *" buf ", size_t buff_size, enum auplugin_mem " how ");"
 .SH DESCRIPTION
 .B auplugin_fgets
 reads from
@@ -34,6 +38,25 @@ indicates whether end of file was reached on
 .B auplugin_fgets_clear
 resets the internal buffer and EOF state, discarding any stored text.
 .PP
+.B auplugin_setvbuf
+points the internal buffer at
+.I buf
+and sets how it will be released when
+.B auplugin_fgets_destroy
+is called. The
+.I how
+parameter should be one of
+.B MEM_MALLOC,
+.B MEM_MMAP,
+or
+.B MEM_SELF_MANAGED.
+The default is
+.B MEM_SELF_MANAGED
+which means no action is taken on the memory block.
+The reentrant form
+.B auplugin_setvbuf_r
+operates on an explicit state handle.
+.PP
 These functions maintain static state and are therefore not thread safe.
 .SH RETURN VALUE
 .B auplugin_fgets