Refactor string handling.

2 files changed, 21 insertions, 18 deletions

diff --git a/asm.peg b/asm.peg
index 3e396c3..a1d517f 100644
--- a/asm.peg
+++ b/asm.peg
@@ -45,7 +45,6 @@ instr =
   | i:sub   { $$ = i; }
   | i:xor   { $$ = i; }
 
-
 jmp = 
   "jmp" ws t:ident 
   { $$.jmp = (Jmp){ .kind = ASM_JMP, .target=t.ident.name } ; }
@@ -241,7 +240,17 @@ r64 =
   | "%r14" ![lwb] { $$ = REG(ASM_R14); }
   | "%r15" ![lwb] { $$ = REG(ASM_R15); }
 
-string = '"' <(('\\\"')|( !'"' .))*> '"' { $$.string = decodestring(yytext); }
+# We disallow newlines in our strings, it is simpler for error messages.
+string = '"' <(string-escape | ( ! '\n' ! '\\' !'"' .))*> '"'
+         { $$.string = decodestring(yytext); }
+
+string-escape = '\\' (
+    '\\'
+  | '"'
+  | [nrt]
+  | 'x' [0-9A-Fa-f]+
+  | [0-7][0-7][0-7]
+)
 
 ident = 
   <[._a-zA-Z][._a-zA-Z0-9]*>
diff --git a/main.c b/main.c
index 5725569..70fad61 100644
--- a/main.c
+++ b/main.c
@@ -151,25 +151,26 @@ static String decodestring(char *s) {
   size_t cap = 0;
   uint8_t *data = NULL;
   uint8_t c = 0;
+  
+  /* The string is already validated by the parser so we omit some checks*/
   while (*s) {
     if (*s == '\\') {
       s++;
-      if (!*s) {
-        lfatal("bad escape in string");
-      } else if (*s >= '0' && *s <= '7') {
+      if (*s >= '0' && *s <= '7') {
         c = strtoul(s, &end, 8);
         s += 3;
-        if (s != end)
-          lfatal("invalid octal sequence");
       } else if (*s == 'x') {
         s++;
         c = strtoul(s, &end, 16);
-        if (s == end)
-          lfatal("invalid hex sequence");
         s = end;
+      } else if (*s == 'r') {
+        c = '\r';
+      } else if (*s == 'n') {
+        c = '\n';
+      } else if (*s == 't') {
+        c = '\t';
       } else {
-        c = *s;
-        s++;
+        unreachable();
       }
     } else {
       c = *s;
@@ -253,16 +254,9 @@ static void sl(uint32_t l) {
 /* Convert an AsmKind to register bits in reg/rm style.  */
 static uint8_t regbits(AsmKind k) { return (k - (ASM_REG_BEGIN + 1)) % 16; }
 
-/* Is a register. */
 static uint8_t isreg(AsmKind k) { return k > ASM_REG_BEGIN && k < ASM_REG_END; }
-
-/* Is an r$n style register variant.  */
 static uint8_t isreg8(AsmKind k) { return k >= ASM_AL && k <= ASM_R15B; }
-
-/* Is an r$n style register variant.  */
 static uint8_t isreg16(AsmKind k) { return k >= ASM_AX && k <= ASM_R15W; }
-
-/* Is an r$n style register variant.  */
 static uint8_t isreg64(AsmKind k) { return k >= ASM_RAX && k <= ASM_R15; }
 
 /* Is an r$n style register variant.  */