io-util: split out "struct iovec" related calls into their own .c/.h files

This is preparation for #28891, which adds a bunch more helpers around
"struct iovec", at which point this really deserves its own .c/.h file.

The idea is that we sooner or later can consider "struct iovec" as an
entirely generic mechanism to reference some binary blob, and is the
go-to type for this purpose whenever we need one.

src/basic/audit-util.c

@@ -10,7 +10,7 @@
 #include "audit-util.h"
 #include "fd-util.h"
 #include "fileio.h"
-#include "io-util.h"
+#include "iovec-util.h"
 #include "macro.h"
 #include "parse-util.h"
 #include "process-util.h"

src/basic/io-util.c

@@ -7,6 +7,7 @@
 
 #include "errno-util.h"
 #include "io-util.h"
+#include "iovec-util.h"
 #include "string-util.h"
 #include "time-util.h"
 
@@ -305,23 +306,6 @@ ssize_t sparse_write(int fd, const void *p, size_t sz, size_t run_length) {
         return q - (const uint8_t*) p;
 }
 
-char* set_iovec_string_field(struct iovec *iovec, size_t *n_iovec, const char *field, const char *value) {
-        char *x;
-
-        x = strjoin(field, value);
-        if (x)
-                iovec[(*n_iovec)++] = IOVEC_MAKE_STRING(x);
-        return x;
-}
-
-char* set_iovec_string_field_free(struct iovec *iovec, size_t *n_iovec, const char *field, char *value) {
-        char *x;
-
-        x = set_iovec_string_field(iovec, n_iovec, field, value);
-        free(value);
-        return x;
-}
-
 struct iovec_wrapper *iovw_new(void) {
         return malloc0(sizeof(struct iovec_wrapper));
 }
@@ -429,13 +413,3 @@ rollback:
         target->count = original_count;
         return r;
 }
-
-void iovec_array_free(struct iovec *iov, size_t n) {
-        if (!iov)
-                return;
-
-        for (size_t i = 0; i < n; i++)
-                free(iov[i].iov_base);
-
-        free(iov);
-}

src/basic/io-util.h

@@ -28,38 +28,6 @@ int fd_wait_for_event(int fd, int event, usec_t timeout);
 
 ssize_t sparse_write(int fd, const void *p, size_t sz, size_t run_length);
 
-static inline size_t IOVEC_TOTAL_SIZE(const struct iovec *i, size_t n) {
-        size_t r = 0;
-
-        for (size_t j = 0; j < n; j++)
-                r += i[j].iov_len;
-
-        return r;
-}
-
-static inline bool IOVEC_INCREMENT(struct iovec *i, size_t n, size_t k) {
-        /* Returns true if there is nothing else to send (bytes written cover all of the iovec),
-         * false if there's still work to do. */
-
-        for (size_t j = 0; j < n; j++) {
-                size_t sub;
-
-                if (i[j].iov_len == 0)
-                        continue;
-                if (k == 0)
-                        return false;
-
-                sub = MIN(i[j].iov_len, k);
-                i[j].iov_len -= sub;
-                i[j].iov_base = (uint8_t*) i[j].iov_base + sub;
-                k -= sub;
-        }
-
-        assert(k == 0); /* Anything else would mean that we wrote more bytes than available,
-                         * or the kernel reported writing more bytes than sent. */
-        return true;
-}
-
 static inline bool FILE_SIZE_VALID(uint64_t l) {
         /* ftruncate() and friends take an unsigned file size, but actually cannot deal with file sizes larger than
          * 2^63 since the kernel internally handles it as signed value. This call allows checking for this early. */
@@ -78,17 +46,6 @@ static inline bool FILE_SIZE_VALID_OR_INFINITY(uint64_t l) {
 
 }
 
-#define IOVEC_NULL (struct iovec) {}
-#define IOVEC_MAKE(base, len) (struct iovec) { .iov_base = (base), .iov_len = (len) }
-#define IOVEC_MAKE_STRING(string)               \
-        ({                                      \
-                char *_s = (char*) (string);    \
-                IOVEC_MAKE(_s, strlen(_s));     \
-        })
-
-char* set_iovec_string_field(struct iovec *iovec, size_t *n_iovec, const char *field, const char *value);
-char* set_iovec_string_field_free(struct iovec *iovec, size_t *n_iovec, const char *field, char *value);
-
 struct iovec_wrapper {
         struct iovec *iovec;
         size_t count;
@@ -123,5 +80,3 @@ int iovw_put_string_field_free(struct iovec_wrapper *iovw, const char *field, ch
 void iovw_rebase(struct iovec_wrapper *iovw, char *old, char *new);
 size_t iovw_size(struct iovec_wrapper *iovw);
 int iovw_append(struct iovec_wrapper *target, const struct iovec_wrapper *source);
-
-void iovec_array_free(struct iovec *iov, size_t n);

src/basic/iovec-util.c

@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "iovec-util.h"
+#include "string-util.h"
+
+
+char* set_iovec_string_field(struct iovec *iovec, size_t *n_iovec, const char *field, const char *value) {
+        char *x;
+
+        assert(iovec);
+        assert(n_iovec);
+
+        x = strjoin(field, value);
+        if (x)
+                iovec[(*n_iovec)++] = IOVEC_MAKE_STRING(x);
+        return x;
+}
+
+char* set_iovec_string_field_free(struct iovec *iovec, size_t *n_iovec, const char *field, char *value) {
+        char *x;
+
+        assert(iovec);
+        assert(n_iovec);
+
+        x = set_iovec_string_field(iovec, n_iovec, field, value);
+        free(value);
+        return x;
+}
+
+void iovec_array_free(struct iovec *iov, size_t n) {
+        if (!iov)
+                return;
+
+        for (size_t i = 0; i < n; i++)
+                free(iov[i].iov_base);
+
+        free(iov);
+}

src/basic/iovec-util.h

@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <stdbool.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+
+#include "macro.h"
+
+static inline size_t IOVEC_TOTAL_SIZE(const struct iovec *i, size_t n) {
+        size_t r = 0;
+
+        for (size_t j = 0; j < n; j++)
+                r += i[j].iov_len;
+
+        return r;
+}
+
+static inline bool IOVEC_INCREMENT(struct iovec *i, size_t n, size_t k) {
+        /* Returns true if there is nothing else to send (bytes written cover all of the iovec),
+         * false if there's still work to do. */
+
+        for (size_t j = 0; j < n; j++) {
+                size_t sub;
+
+                if (i[j].iov_len == 0)
+                        continue;
+                if (k == 0)
+                        return false;
+
+                sub = MIN(i[j].iov_len, k);
+                i[j].iov_len -= sub;
+                i[j].iov_base = (uint8_t*) i[j].iov_base + sub;
+                k -= sub;
+        }
+
+        assert(k == 0); /* Anything else would mean that we wrote more bytes than available,
+                         * or the kernel reported writing more bytes than sent. */
+        return true;
+}
+
+#define IOVEC_NULL (struct iovec) {}
+#define IOVEC_MAKE(base, len) (struct iovec) { .iov_base = (base), .iov_len = (len) }
+#define IOVEC_MAKE_STRING(string)               \
+        ({                                      \
+                char *_s = (char*) (string);    \
+                IOVEC_MAKE(_s, strlen(_s));     \
+        })
+
+char* set_iovec_string_field(struct iovec *iovec, size_t *n_iovec, const char *field, const char *value);
+char* set_iovec_string_field_free(struct iovec *iovec, size_t *n_iovec, const char *field, char *value);
+
+void iovec_array_free(struct iovec *iov, size_t n);

src/basic/log.c

@@ -21,7 +21,7 @@
 #include "errno-util.h"
 #include "fd-util.h"
 #include "format-util.h"
-#include "io-util.h"
+#include "iovec-util.h"
 #include "log.h"
 #include "macro.h"
 #include "missing_syscall.h"

src/basic/meson.build

@@ -44,6 +44,7 @@ basic_sources = files(
         'initrd-util.c',
         'inotify-util.c',
         'io-util.c',
+        'iovec-util.c',
         'ioprio-util.c',
         'label.c',
         'limits-util.c',