libsysprof-analyze: add inlined line reader

This is a bit nicer than the allocating form we have elsewhere.

src/libsysprof-analyze/line-reader-private.h

@@ -0,0 +1,94 @@
+/* line-reader-private.h
+ *
+ * Copyright 2015-2023 Christian Hergert <christian@hergert.me>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include <glib.h>
+#include <string.h>
+
+G_BEGIN_DECLS
+
+typedef struct _LineReader
+{
+  char   *contents;
+  gsize   length;
+  gssize  pos;
+} LineReader;
+
+static inline void
+line_reader_init (LineReader *reader,
+                  char       *contents,
+                  gssize      length)
+{
+  g_assert (reader != NULL);
+
+  if (length < 0)
+    length = strlen (contents);
+
+  if (contents != NULL)
+    {
+      reader->contents = contents;
+      reader->length = length;
+      reader->pos = 0;
+    }
+  else
+    {
+      reader->contents = NULL;
+      reader->length = 0;
+      reader->pos = 0;
+    }
+}
+
+static inline char *
+line_reader_next (LineReader *reader,
+                  gsize      *length)
+{
+  char *ret = NULL;
+
+  g_assert (reader != NULL);
+  g_assert (length != NULL);
+
+  if ((reader->contents == NULL) || (reader->pos >= reader->length))
+    {
+      *length = 0;
+      return NULL;
+    }
+
+  ret = &reader->contents [reader->pos];
+
+  for (; reader->pos < reader->length; reader->pos++)
+    {
+      if (reader->contents [reader->pos] == '\n')
+        {
+          *length = &reader->contents [reader->pos] - ret;
+          /* Ingore the \r in \r\n if provided */
+          if (*length > 0 && reader->pos > 0 && reader->contents [reader->pos - 1] == '\r')
+            (*length)--;
+          reader->pos++;
+          return ret;
+        }
+    }
+
+  *length = &reader->contents [reader->pos] - ret;
+
+  return ret;
+}
+
+G_END_DECLS