evalstr: add helper functions to compute expressions from a stringevalstr

In far too many places, especially in directives, we don't accept an
actual expression because, realistically, there have been way too many
hoops to jump through to do so. Add helper functions to make that far
easier.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 60 insertions, 0 deletions

diff --git a/asm/evalstr.h b/asm/evalstr.h
new file mode 100644
index 00000000..4d06628b
--- /dev/null
+++ b/asm/evalstr.h
@@ -0,0 +1,60 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *   Copyright 2018 The NASM Authors - All Rights Reserved
+ *   See the file AUTHORS included with the NASM distribution for
+ *   the specific copyright holders.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following
+ *   conditions are met:
+ *
+ *   * Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *   * Redistributions in binary form must reproduce the above
+ *     copyright notice, this list of conditions and the following
+ *     disclaimer in the documentation and/or other materials provided
+ *     with the distribution.
+ *
+ *     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ *     CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ *     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ *     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ *     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ *     CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *     SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ *     NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ *     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ *     HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *     CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ *     OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+ *     EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * Wrappers around stdscan() and evaluate() for computing expressions
+ * directly from strings.
+ */
+
+#ifndef NASM_EVALSTR_H
+#define NASM_EVALSTR_H
+
+#include "compiler.h"
+
+/*
+ * Evaluate a string, returning the offset component. The string pointer
+ * is advanced to the beginning of the first token following the
+ * end of the expression.
+ *
+ * If the "segment" and/or "wrt" pointers are NULL, then those
+ * components are explicitly forbidden and will throw an error.
+ */
+int64_t evaluate_str(char **str, bool crit, int32_t *segment, int32_t *wrt);
+
+/*
+ * Evaluate a size expression: a pure integer, but size specifiers like
+ * BYTE are treated like integer constants.
+ */
+int64_t evaluate_size(char **str, bool crit);
+
+#endif  /* NASM_EVALSTR_H */