feat(string): add ssh_string_from_data function to create ssh_string from data buffer

Signed-off-by: Praneeth Sarode <praneethsarode@gmail.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

include/libssh/libssh.h

@@ -844,6 +844,7 @@ LIBSSH_API int ssh_string_fill(ssh_string str, const void *data, size_t len);
     do { if ((x) != NULL) { ssh_string_free(x); x = NULL; } } while(0)
 LIBSSH_API void ssh_string_free(ssh_string str);
 LIBSSH_API ssh_string ssh_string_from_char(const char *what);
+LIBSSH_API ssh_string ssh_string_from_data(const void *data, size_t len);
 LIBSSH_API size_t ssh_string_len(ssh_string str);
 LIBSSH_API ssh_string ssh_string_new(size_t size);
 LIBSSH_API const char *ssh_string_get_char(ssh_string str);

src/libssh.map

@@ -492,5 +492,6 @@ LIBSSH_AFTER_4_10_0
         sshsig_sign;
         sshsig_verify;
         ssh_string_cmp;
+        ssh_string_from_data;
 } LIBSSH_4_10_0;
 

src/string.c

@@ -128,6 +128,45 @@ struct ssh_string_struct *ssh_string_from_char(const char *what)
     return ptr;
 }
 
+/**
+ * @brief Create a ssh string from an arbitrary data buffer.
+ *
+ * Allocates a new SSH string of length `len` and copies the provided data
+ * into it. If len is 0, returns an empty SSH string. When len > 0, data
+ * must not be NULL.
+ *
+ * @param[in] data     Pointer to the data buffer to copy from. May be NULL
+ *                     only when len == 0.
+ * @param[in] len      Length of the data buffer to copy.
+ *
+ * @return             The newly allocated string, NULL on error.
+ */
+struct ssh_string_struct *ssh_string_from_data(const void *data, size_t len)
+{
+    struct ssh_string_struct *s = NULL;
+    int rc;
+
+    if (len > 0 && data == NULL) {
+        errno = EINVAL;
+        return NULL;
+    }
+
+    s = ssh_string_new(len);
+    if (s == NULL) {
+        return NULL;
+    }
+
+    if (len > 0) {
+        rc = ssh_string_fill(s, data, len);
+        if (rc != 0) {
+            ssh_string_free(s);
+            return NULL;
+        }
+    }
+
+    return s;
+}
+
 /**
  * @brief Return the size of a SSH string.
  *