1 files changed, 122 insertions, 0 deletions
diff --git a/src/fspec/ragel/lexer-expr.rl b/src/fspec/ragel/lexer-expr.rl
new file mode 100644
index 0000000..2975043
--- /dev/null
+++ b/src/fspec/ragel/lexer-expr.rl
@@ -0,0 +1,122 @@
+#include "lexer-expr.h"
+#include "lexer-stack.h"
+#include "util/ragel/ragel.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <assert.h>
+#include <err.h>
+
+static uint8_t
+precedence(char op)
+{
+   switch (op) {
+      case '^': return 4;
+      case '*': return 3;
+      case '/': return 3;
+      case '+': return 2;
+      case '-': return 2;
+   }
+   errx(EXIT_FAILURE, "unknown operator %c for precedence", op);
+   return 0;
+}
+
+static size_t
+pop(char cur, char *mstack, size_t open)
+{
+   static char cvar = 'a';
+
+   // 1 + 2 + 4 + 3 * 2 / 2 * 2 * 2 - 2 * 2 + 5;
+   while (open >= 3) {
+      const char last_op = mstack[open - 2];
+      const uint8_t last_prio = precedence(last_op);
+      const uint8_t new_prio = precedence(cur);
+
+      if (last_prio <= new_prio)
+         break;
+
+      printf("%c = ", cvar);
+      for (size_t i = open - 3; i < open; ++i)
+         printf("%c ", mstack[i]);
+      puts(";");
+      open -= 3;
+
+      mstack[open++] = cvar;
+      ++cvar;
+   }
+
+   return open;
+}
+
+%%{
+   machine fspec_expr;
+   include fspec_stack "lexer-stack.rl";
+   variable p ragel.p;
+   variable pe ragel.pe;
+   variable eof ragel.eof;
+   write data noerror nofinal;
+
+   action op {
+      open = pop(fc, mstack, open);
+      mstack[open++] = fc;
+   }
+
+   logical_operators = '&&' | '||' | '==' | '<' | '>' | '<=' | '>=';
+   calc_operators = '-' | '+' | '/' | '*' | '%';
+   bitwise_operators = '&' | '|' | '^' | '<<' | '>>';
+
+   main := |*
+      '+' => op;
+      '/' => op;
+      '*' => op;
+      '-' => op;
+      '^' => op;
+      stack_num => { mstack[open++] = fc;};
+      '(' => { };
+      ')' => { };
+      ' ';
+      ';' => {
+         printf("v = ");
+         for (size_t i = 0; i < open; ++i)
+            printf("%c ", mstack[i]);
+         puts(";");
+      };
+      *|;
+}%%
+
+
+bool
+fspec_expr_parse(struct fspec_expr *expr, const char *name)
+{
+   int cs, act;
+   const char *ts, *te;
+   (void)ts;
+
+   size_t open = 0;
+   char mstack[25];
+
+   %% write init;
+
+   (void)fspec_expr_en_main;
+   assert(expr);
+   assert(expr->ops.read);
+   assert(expr->ops.write);
+   assert(expr->mem.input.data && expr->mem.input.len);
+   assert(expr->mem.input.len <= (size_t)~0 && "input storage size exceeds size_t range");
+
+   char var[256];
+   struct stack stack = { .var.buf.mem = { .data = var, .len = sizeof(var) } };
+   struct ragel ragel = { .name = name, .lineno = 1 };
+
+   // static const fspec_num version = 0;
+
+   struct fspec_mem input = expr->mem.input;
+   for (bool eof = false; !ragel.error && !eof;) {
+      const size_t bytes = expr->ops.read(expr, input.data, 1, input.len);
+      const struct ragel_mem rl = { .data = input.data, .end = (char*)input.data + bytes };
+      ragel_feed_input(&ragel, (eof = (bytes < input.len)), &rl);
+      %% write exec;
+   }
+
+   return !ragel.error;
+}