diff --git a/epicardium/epicardium.h b/epicardium/epicardium.h
index 84071d042c85643dfc181549f038e46c9c4b354a..f2398732994160a13b949f79825060221d53587f 100644
--- a/epicardium/epicardium.h
+++ b/epicardium/epicardium.h
@@ -145,6 +145,7 @@ typedef _Bool bool;
#define API_CONFIG_GET_STRING 0x130
#define API_CONFIG_GET_INTEGER 0x131
#define API_CONFIG_GET_BOOLEAN 0x132
+#define API_CONFIG_SET_STRING 0x133
/* clang-format on */
typedef uint32_t api_int_id_t;
@@ -2060,5 +2061,21 @@ API(API_CONFIG_GET_BOOLEAN, int epic_config_get_boolean(const char *key, bool *v
API(API_CONFIG_GET_STRING, int epic_config_get_string(const char *key, char *buf, size_t buf_len));
+/**
+ * Write a string to the configuration file.
+ *
+ * :param char* key: Name of the option to write
+ * :param char* value: The value to write
+ * :return: `0` on success or a negative value if an error occured. Possivle
+ * errors:
+ *
+ * - ``-EINVAL``: Parameters out of range
+ * - ``-ENOENT``: Key already exists but can not be read
+ * - ``-EIO`` : Unspecified I/O error
+ * - Any fopen/fread/fwrite/fclose related error code
+ *
+ * .. versionadded:: 1.16
+ */
+API(API_CONFIG_SET_STRING, int epic_config_set_string(const char *key, const char *value));
#endif /* _EPICARDIUM_H */
diff --git a/epicardium/modules/config.c b/epicardium/modules/config.c
index 922dae657fe78be03280d5145bba651c0b6cbfd6..6874318a1e3f0bdfa58cd61dd4f81b584eaa26ff 100644
--- a/epicardium/modules/config.c
+++ b/epicardium/modules/config.c
@@ -11,6 +11,7 @@
#include <stdlib.h>
#include <unistd.h>
#include <stddef.h>
+#include <stdio.h>
#define MAX_LINE_LENGTH 80
#define KEYS_PER_BLOCK 16
@@ -381,3 +382,222 @@ bool config_get_boolean_with_default(const char *key, bool default_value)
return value;
}
}
+
+// TODO: don't allow things like "execute_elf" to be set
+int epic_config_set_string(const char *key, const char *value)
+{
+ config_slot *slot = find_config_slot(key);
+ bool present = slot && slot->value_offset;
+ int ret = 0;
+
+ if (snprintf(NULL, 0, "\n%s = %s\n", key, value) > MAX_LINE_LENGTH) {
+ return -EINVAL;
+ }
+
+ if (!present) {
+ /* Easy case: We simply add the new option at the
+ * end of the file. */
+
+ char buf[MAX_LINE_LENGTH];
+ /* Leading new line because I'm lazy */
+ ret = snprintf(buf, sizeof(buf), "\n%s = %s\n", key, value);
+
+ if (ret < 0 || ret >= (int)sizeof(buf)) {
+ return -EINVAL;
+ }
+
+ int fd = epic_file_open("card10.cfg", "a");
+ if (fd < 0) {
+ LOG_DEBUG(
+ "card10.cfg",
+ "open for appending failed: %s (%d)",
+ strerror(-fd),
+ fd
+ );
+ return fd;
+ }
+
+ int write_ret = epic_file_write(fd, buf, strlen(buf));
+ if (write_ret < 0) {
+ LOG_DEBUG(
+ "card10.cfg",
+ "writing failed: %s (%d)",
+ strerror(-write_ret),
+ write_ret
+ );
+ }
+
+ if (write_ret < (int)strlen(buf)) {
+ LOG_DEBUG(
+ "card10.cfg",
+ "writing failed to write all bytes (%d of %d)",
+ write_ret,
+ strlen(buf)
+ );
+ }
+
+ ret = epic_file_close(fd);
+
+ if (ret < 0) {
+ LOG_DEBUG(
+ "card10.cfg",
+ "close failed: %s (%d)",
+ strerror(-ret),
+ ret
+ );
+ }
+ if (write_ret < 0) {
+ return write_ret;
+ }
+ if (ret < 0) {
+ return ret;
+ }
+ if (write_ret < (int)strlen(buf)) {
+ LOG_DEBUG(
+ "card10.cfg",
+ "writing failed to write all bytes (%d of %d)",
+ write_ret,
+ strlen(buf)
+ );
+ return -EIO;
+ }
+ } else {
+ /* Complex case: The value is already somewhere in the file.
+ * We do not want to lose existing formatting or comments.
+ * Solution: Copy parts of the file, insert new value, copy
+ * rest, rename.
+ */
+ char buf[128];
+ int fd1 = -1;
+ int fd2 = -1;
+ ret = epic_config_get_string(key, buf, sizeof(buf));
+
+ if (ret < 0) {
+ LOG_DEBUG(
+ "card10.cfg",
+ "could not read old value (%d)",
+ ret
+ );
+ goto out;
+ }
+
+ int old_len = strlen(buf);
+
+ fd1 = epic_file_open("card10.cfg", "r");
+ if (fd1 < 0) {
+ LOG_DEBUG(
+ "card10.cfg",
+ "open for read failed: %s (%d)",
+ strerror(-fd1),
+ fd1
+ );
+ ret = fd1;
+ goto out;
+ }
+
+ fd2 = epic_file_open("card10.nfg", "w");
+ if (fd2 < 0) {
+ LOG_DEBUG(
+ "card10.nfg",
+ "open for writing failed: %s (%d)",
+ strerror(-fd2),
+ fd2
+ );
+ ret = fd2;
+ goto out;
+ }
+
+ /* Copy over slot->value_offset bytes */
+ int i = slot->value_offset;
+ while (i > 0) {
+ int n = i > (int)sizeof(buf) ? (int)sizeof(buf) : i;
+ ret = epic_file_read(fd1, buf, n);
+ if (ret < 0) {
+ LOG_DEBUG(
+ "card10.cfg",
+ "read failed: rc: %d",
+ ret
+ );
+ goto out;
+ }
+
+ int ret2 = epic_file_write(fd2, buf, ret);
+
+ if (ret2 < 0) {
+ ret = ret2;
+ LOG_DEBUG(
+ "card10.nfg",
+ "write failed: rc: %d",
+ ret
+ );
+ goto out;
+ }
+ i -= ret;
+ }
+
+ /* Insert new value into the new file */
+ ret = epic_file_write(fd2, value, strlen(value));
+ if (ret < 0) {
+ LOG_DEBUG("card10.nfg", "write failed: rc: %d", ret);
+ goto out;
+ }
+
+ /* Skip the old value inside the old file */
+ epic_file_seek(fd1, old_len, SEEK_CUR);
+
+ /* Copy the rest of the old file to the new file */
+ while (true) {
+ int ret = epic_file_read(fd1, buf, sizeof(buf));
+
+ if (ret == 0) {
+ break;
+ }
+
+ if (ret < 0) {
+ LOG_DEBUG(
+ "card10.cfg",
+ "read failed: rc: %d",
+ ret
+ );
+ goto out;
+ }
+
+ int ret2 = epic_file_write(fd2, buf, ret);
+
+ if (ret2 < 0) {
+ ret = ret2;
+ LOG_DEBUG(
+ "card10.nfg",
+ "write failed: rc: %d",
+ ret
+ );
+ goto out;
+ }
+
+ if (ret < (int)sizeof(buf)) {
+ break;
+ }
+ }
+
+ out:
+ if (fd1 >= 0) {
+ epic_file_close(fd1);
+ }
+ if (fd2 >= 0) {
+ int ret2 = epic_file_close(fd2);
+ if (ret >= 0) {
+ ret = ret2;
+ }
+ }
+
+ if (ret >= 0) {
+ epic_file_unlink("card10.cfg");
+ epic_file_rename("card10.nfg", "card10.cfg");
+ }
+ }
+
+ /* Reload config so the new key or the changed value is available */
+ load_config();
+
+ return ret < 0 ? ret : 0;
+}