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Fixed world's worst recursive descent parser (issue #5)

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chad
2014-10-08 16:35:15 -04:00
parent 1f34e759bc
commit 65c9aeadc5
1 changed files with 44 additions and 26 deletions
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68
src/obj.cpp
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@@ -41,15 +41,13 @@ static int skip_parens(const string &s, int i) {
} }
// Probably the worst recursive descent parser ever written, but it's an easy // Probably the worst recursive descent parser ever written, but it's an easy
// way to make our assembly language pretty. // way to make our assembly language prettier.
static uint64_t readParenExpression(const string &s, const map<string, Word> &d, static uint64_t rPE(bool &v, const string &s, const map<string, Word> &d,
int start=0, int end=-1) int start, int end)
{ {
uint64_t (* const rPE)(const string&, const map<string, Word>&, int, int) D(2, "rPE(" << v << ", " << s << ", d, " << start << ", " << end << ");");
= readParenExpression;
if (end == start) return 0;
if (end==-1) end = s.length(); if (end == start) { v = false; return 0; }
while (isspace(s[start])) start++; while (isspace(s[start])) start++;
while (isspace(s[end-1])) end--; while (isspace(s[end-1])) end--;
@@ -57,29 +55,37 @@ static uint64_t readParenExpression(const string &s, const map<string, Word> &d,
for (int i = start; i < end; i++) { for (int i = start; i < end; i++) {
if (s[i] == '(') { i = skip_parens(s, i); continue; } if (s[i] == '(') { i = skip_parens(s, i); continue; }
if (s[i] == '<') return rPE(s, d, start, i) << rPE(s, d, i+2, end); if (s[i] == '<') return rPE(v, s, d, start, i) << rPE(v, s, d, i+2, end);
if (s[i] == '>') return rPE(s, d, start, i) >> rPE(s, d, i+2, end); if (s[i] == '>') return rPE(v, s, d, start, i) >> rPE(v, s, d, i+2, end);
} }
for (int i = start; i < end; i++) { for (int i = start; i < end; i++) {
if (s[i] == '(') { i = skip_parens(s, i); continue; } if (s[i] == '(') { i = skip_parens(s, i); continue; }
if (s[i] == '+') return rPE(s, d, start, i) + rPE(s, d, i+1, end); if (s[i] == '+') return rPE(v, s, d, start, i) + rPE(v, s, d, i+1, end);
if (s[i] == '-') return rPE(s, d, start, i) - rPE(s, d, i+1, end); if (s[i] == '-') {
if (s[i] == '|') return rPE(s, d, start, i) | rPE(s, d, i+1, end); // If we've already failed, don't try this.
if (s[i] == '^') return rPE(s, d, start, i) ^ rPE(s, d, i+1, end); if (v == false) return 0;
// If it works as a binary -, return that. Otherwise, it's a unary -
uint64_t x(rPE(v, s, d, start, i) - rPE(v, s, d, i+1, end));
if (v) return x;
else v = true;
}
if (s[i] == '|') return rPE(v, s, d, start, i) | rPE(v, s, d, i+1, end);
if (s[i] == '^') return rPE(v, s, d, start, i) ^ rPE(v, s, d, i+1, end);
} }
for (int i = start; i < end; i++) { for (int i = start; i < end; i++) {
if (s[i] == '(') { i = skip_parens(s, i); continue; } if (s[i] == '(') { i = skip_parens(s, i); continue; }
if (s[i] == '*') return rPE(s, d, start, i) * rPE(s, d, i+1, end); if (s[i] == '*') return rPE(v, s, d, start, i) * rPE(v, s, d, i+1, end);
if (s[i] == '/') return rPE(s, d, start, i) / rPE(s, d, i+1, end); if (s[i] == '/') return rPE(v, s, d, start, i) / rPE(v, s, d, i+1, end);
if (s[i] == '%') return rPE(s, d, start, i) % rPE(s, d, i+1, end); if (s[i] == '%') return rPE(v, s, d, start, i) % rPE(v, s, d, i+1, end);
if (s[i] == '&') return rPE(s, d, start, i) & rPE(s, d, i+1, end); if (s[i] == '&') return rPE(v, s, d, start, i) & rPE(v, s, d, i+1, end);
} }
// Unary operators // Unary operators
if (s[start] == '-') return -rPE(s, d, start+1, end); if (s[start] == '-') return -rPE(v, s, d, start+1, end);
if (s[start] == '`') return log2(rPE(s, d, start+1, end)); if (s[start] == '`') return log2(rPE(v, s, d, start+1, end));
if (isdigit(s[start])) { if (isdigit(s[start])) {
unsigned long long u; unsigned long long u;
@@ -87,13 +93,22 @@ static uint64_t readParenExpression(const string &s, const map<string, Word> &d,
return u; return u;
} }
if (s[start] == '(') return rPE(s, d, start+1, end-1); if (s[start] == '(') return rPE(v, s, d, start+1, end-1);
map<string, Word>::const_iterator it = d.find(s.substr(start, end-start)); string label(s.substr(start, end-start));
map<string, Word>::const_iterator it(d.find(label));
if (it != d.end()) return it->second; if (it != d.end()) return it->second;
cout << "Error on " << yyline << ": "; // If nothing else works, set valid to false.
exit(1); v = 0;
return 0;
}
static uint64_t readParenExpression(bool &valid, const string &s,
const map<string, Word> &d)
{
valid = true;
return rPE(valid, s, d, 0, s.length());
} }
int lexerFloatBytes; int lexerFloatBytes;
@@ -355,9 +370,12 @@ Obj *AsmReader::read(std::istream &input) {
default: asmReaderError(yyline, "Unexpected register"); default: asmReaderError(yyline, "Unexpected register");
} }
break; break;
case ASM_T_PEXP: case ASM_T_PEXP: {
// Decode the paren expression. // Decode the paren expression.
yylval.u = readParenExpression(yylval.s, defs); bool valid;
yylval.u = readParenExpression(valid, yylval.s, defs);
if (!valid) asmReaderError(yyline, "Invalid paren expression");
}
case ASM_T_LIT: case ASM_T_LIT:
switch (state) { switch (state) {
case ST_INST1: asmReaderError(yyline, "Unexpected literal"); case ST_INST1: asmReaderError(yyline, "Unexpected literal");