Add line wrapper

Add a tool to wrap lines at words boundaries (spaces) to fit in a
specified number of columns, left-indented by a specified number of
spaces.

app/meson.build

@@ -187,6 +187,7 @@ if get_option('buildtype') == 'debug'
             'tests/test_cli.c',
             'src/cli.c',
             'src/options.c',
+            'src/util/strbuf.c',
             'src/util/str_util.c',
         ]],
         ['test_clock', [
@@ -196,6 +197,7 @@ if get_option('buildtype') == 'debug'
         ['test_control_msg_serialize', [
             'tests/test_control_msg_serialize.c',
             'src/control_msg.c',
+            'src/util/strbuf.c',
             'src/util/str_util.c',
         ]],
         ['test_device_msg_deserialize', [
@@ -211,6 +213,7 @@ if get_option('buildtype') == 'debug'
         ]],
         ['test_strutil', [
             'tests/test_strutil.c',
+            'src/util/strbuf.c',
             'src/util/str_util.c',
         ]],
     ]

app/src/util/str_util.c

@@ -1,9 +1,11 @@
 #include "str_util.h"
 
+#include <assert.h>
 #include <errno.h>
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
+#include "util/strbuf.h"
 
 #ifdef _WIN32
 # include <windows.h>
@@ -209,3 +211,76 @@ utf8_from_wide_char(const wchar_t *ws) {
 }
 
 #endif
+
+char *wrap_lines(const char *input, unsigned columns, unsigned indent) {
+    struct sc_strbuf buf;
+
+    // The output string should not be a lot longer than the input string (just
+    // a few '\n' added), so this initial capacity should almost always avoid
+    // internal realloc() in string buffer
+    size_t cap = strlen(input) * 3 / 2;
+
+    if (!sc_strbuf_init(&buf, cap)) {
+        return false;
+    }
+
+    assert(indent < columns);
+
+#define APPEND(S,N) if (!sc_strbuf_append(&buf, S, N)) goto error
+#define APPEND_CHAR(C) if (!sc_strbuf_append_char(&buf, C)) goto error
+#define APPEND_N(C,N) if (!sc_strbuf_append_n(&buf, C, N)) goto error
+#define APPEND_INDENT() if (indent) APPEND_N(' ', indent)
+
+    APPEND_INDENT();
+
+    // The last separator encountered, it must be inserted only conditionnaly,
+    // depending on the next token
+    char pending = 0;
+
+    // col tracks the current column in the current line
+    size_t col = indent;
+    while (*input) {
+        size_t sep_idx = strcspn(input, "\n ");
+        bool wrap = col + sep_idx > columns;
+
+        char sep = input[sep_idx];
+        if (sep == ' ')
+            sep = ' ';
+
+        if (wrap) {
+            APPEND_CHAR('\n');
+            APPEND_INDENT();
+            col = indent;
+        } else if (pending) {
+            APPEND_CHAR(pending);
+            ++col;
+            if (pending == '\n')
+            {
+                APPEND_INDENT();
+                col = indent;
+            }
+        }
+
+        if (sep_idx) {
+            APPEND(input, sep_idx);
+            col += sep_idx;
+        }
+
+        pending = sep;
+
+        input += sep_idx;
+        if (*input != '\0') {
+            // Skip the separator
+            ++input;
+        }
+    }
+
+    if (pending)
+        APPEND_CHAR(pending);
+
+    return buf.s;
+
+error:
+    free(buf.s);
+    return NULL;
+}

app/src/util/str_util.h

@@ -62,4 +62,8 @@ char *
 utf8_from_wide_char(const wchar_t *s);
 #endif
 
+// Wrap input lines at words boundaries (spaces) so that they fit in 'columns'
+// columns, left-indented by 'indent' spaces
+char *wrap_lines(const char *input, unsigned columns, unsigned indent);
+
 #endif

app/tests/test_strutil.c

@@ -299,6 +299,45 @@ static void test_strlist_contains(void) {
     assert(strlist_contains("xyz", '\0', "xyz"));
 }
 
+static void test_wrap_lines(void) {
+    const char *s = "This is a text to test line wrapping. The lines must be "
+                    "wrapped either at a space or a line break.\n"
+                    "\n"
+                    "This rectangle must remains a rectangle because it is "
+                    "drawn in lines having lengths lower than the specified "
+                    "number of columns:\n"
+                    "  +----+\n"
+                    "  |    |\n"
+                    "  +----+\n";
+
+    //                     |----      1    1    2  2|
+    //                     |0    5    0    5    0  3| <-- 24 columns
+    const char *expected = "    This is a text to\n"
+                           "    test line wrapping.\n"
+                           "    The lines must be\n"
+                           "    wrapped either at a\n"
+                           "    space or a line\n"
+                           "    break.\n"
+                           "    \n"
+                           "    This rectangle must\n"
+                           "    remains a rectangle\n"
+                           "    because it is drawn\n"
+                           "    in lines having\n"
+                           "    lengths lower than\n"
+                           "    the specified number\n"
+                           "    of columns:\n"
+                           "      +----+\n"
+                           "      |    |\n"
+                           "      +----+\n";
+
+    char *formatted = wrap_lines(s, 24, 4);
+    assert(formatted);
+
+    assert(!strcmp(formatted, expected));
+
+    free(formatted);
+}
+
 int main(int argc, char *argv[]) {
     (void) argc;
     (void) argv;
@@ -317,5 +356,6 @@ int main(int argc, char *argv[]) {
     test_parse_integers();
     test_parse_integer_with_suffix();
     test_strlist_contains();
+    test_wrap_lines();
     return 0;
 }