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feat: add to support non-capturing group syntax #35

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feat: add to support non-capturing group syntax #35

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9abe8bb
feat: provide group struct for Capture Expr
elton2048 Sep 16, 2024
f14d10c
feat: add to support non-capturing group syntax
elton2048 Sep 17, 2024
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10 changes: 9 additions & 1 deletion src/compile.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -187,6 +187,8 @@ pub const Compiler = struct {

fn nextCaptureIndex(c: *Compiler) usize {
const s = c.capture_index;
// each capture contains start and end pos, hence add two for
// each iteration
c.capture_index += 2;
return s;
}
Expand Down Expand Up @@ -350,13 +352,19 @@ pub const Compiler = struct {
// 3: restore 1, 4
// ...

if (!subexpr.capturing) {
const p = try c.compileInternal(subexpr.expr);
const hole = p.hole;
return Patch{ .hole = hole, .entry = p.entry };
}

// Create a partial instruction with a hole outgoing at the current location.
const entry = c.insts.items.len;

const index = c.nextCaptureIndex();

try c.pushCompiled(Instruction.new(entry + 1, InstructionData{ .Save = index }));
const p = try c.compileInternal(subexpr);
const p = try c.compileInternal(subexpr.expr);
c.fillToNext(p.hole);

const h = try c.pushHole(InstHole{ .Save = index + 1 });
Expand Down
2 changes: 1 addition & 1 deletion src/debug.zig
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Expand Up @@ -56,7 +56,7 @@ fn dumpExprIndent(e: Expr, indent: usize) void {
},
Expr.Capture => |subexpr| {
debug.print("{s}\n", .{@tagName(e)});
dumpExprIndent(subexpr.*, indent + 1);
dumpExprIndent(subexpr.*.expr.*, indent + 1);
},
Expr.Repeat => |repeat| {
debug.print("{s}(min={d}, max={?d}, greedy={any})\n", .{ @tagName(e), repeat.min, repeat.max, repeat.greedy });
Expand Down
68 changes: 60 additions & 8 deletions src/parse.zig
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Expand Up @@ -48,6 +48,11 @@ pub const Assertion = enum {
NotWordBoundaryAscii,
};

/// Extra attributes for group expression.
pub const GroupAttributes = struct {
capturing: bool,
};

/// A single node of an expression tree.
pub const Expr = union(enum) {
// Empty match (\w assertion)
Expand All @@ -57,7 +62,7 @@ pub const Expr = union(enum) {
// . character
AnyCharNotNL,
// Capture group
Capture: *Expr,
Capture: *Group,
// *, +, ?
Repeat: Repeater,
// Character class [a-z0-9]
Expand All @@ -67,7 +72,7 @@ pub const Expr = union(enum) {
// |
Alternate: ArrayList(*Expr),
// Pseudo stack operator to define start of a capture
PseudoLeftParen,
PseudoLeftParen: GroupAttributes,

pub fn isByteClass(re: *const Expr) bool {
switch (re.*) {
Expand Down Expand Up @@ -95,6 +100,13 @@ pub const Expr = union(enum) {
}
};

/// A single node of a group. The group could include different modifiers
/// by Perl flag for further features like non-capturing group.
pub const Group = struct {
expr: *Expr,
capturing: bool,
};

// Private in fmt.
fn charToDigit(c: u8, radix: u8) !u8 {
const value = switch (c) {
Expand Down Expand Up @@ -243,6 +255,7 @@ pub const ParseError = error{
InvalidHexDigit,
InvalidOctalDigit,
UnrecognizedEscapeCode,
UnimplementedModifier,
};

pub const ParserOptions = struct {
Expand Down Expand Up @@ -326,6 +339,10 @@ pub const Parser = struct {
return try p.arena.allocator().create(Expr);
}

fn createGroup(p: *Parser) !*Group {
return try p.arena.allocator().create(Group);
}

pub fn parse(p: *Parser, re: []const u8) !*Expr {
p.it = StringIterator.init(re);
// Shorter alias
Expand Down Expand Up @@ -394,8 +411,24 @@ pub const Parser = struct {
// Don't handle alternation just yet, parentheses group together arguments into
// a sub-expression only.
'(' => {
var capturing = true;
if (it.peekIs('?')) {
// Advance and discard
_ = it.next();
if (it.peekIs(':')) {
// Advance and discard
_ = it.next();
capturing = false;
} else {
// NOTE: Other modifiers are considered not implemented
return error.UnimplementedModifier;
}
}

const r = try p.createExpr();
r.* = Expr{ .PseudoLeftParen = undefined };
r.* = Expr{ .PseudoLeftParen = .{
.capturing = capturing,
} };
try p.stack.append(r);
},
')' => {
Expand Down Expand Up @@ -435,16 +468,29 @@ pub const Parser = struct {
return error.UnopenedParentheses;
}

// pop the left parentheses that must now exist
debug.assert(p.stack.pop().* == Expr.PseudoLeftParen);
const next_e = p.stack.pop().*;
var capturing: bool = undefined;
switch (next_e) {
// pop the left parentheses that must now exist
.PseudoLeftParen => |e_paren| {
capturing = e_paren.capturing;
},
else => unreachable,
}

const group = try p.createGroup();
group.* = Group{
.expr = e,
.capturing = capturing,
};

const r = try p.createExpr();
r.* = Expr{ .Capture = e };
r.* = Expr{ .Capture = group };
try p.stack.append(r);
break;
},
// Existing parentheses, push new alternation
.PseudoLeftParen => {
.PseudoLeftParen => |e_paren| {
mem.reverse(*Expr, concat.items);

const ra = try p.createExpr();
Expand All @@ -458,8 +504,14 @@ pub const Parser = struct {
ra.* = Expr{ .Concat = concat };
}

const group = try p.createGroup();
group.* = Group{
.expr = ra,
.capturing = e_paren.capturing,
};

const r = try p.createExpr();
r.* = Expr{ .Capture = ra };
r.* = Expr{ .Capture = group };
try p.stack.append(r);
break;
},
Expand Down
2 changes: 1 addition & 1 deletion src/parse_test.zig
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Expand Up @@ -84,7 +84,7 @@ fn reprIndent(out: *StaticWriter, e: *Expr, indent: usize) anyerror!void {
},
Expr.Capture => |subexpr| {
try out.writer().print("cap\n", .{});
try reprIndent(out, subexpr, indent + 1);
try reprIndent(out, subexpr.*.expr, indent + 1);
},
Expr.Repeat => |repeat| {
try out.writer().print("rep(", .{});
Expand Down
20 changes: 20 additions & 0 deletions src/regex_test.zig
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Expand Up @@ -141,6 +141,26 @@ test "regex captures" {

debug.assert(mem.eql(u8, "ab0123", caps.sliceAt(0).?));
debug.assert(mem.eql(u8, "0123", caps.sliceAt(1).?));

var r_non_capturing_1 = try Regex.compile(std.testing.allocator, "ab(?:\\d+)");
defer r_non_capturing_1.deinit();

debug.assert(try r_non_capturing_1.partialMatch("xxxxab0123a"));

var caps_non_capturing_1 = (try r_non_capturing_1.captures("xxxxab0123a")).?;
defer caps_non_capturing_1.deinit();

debug.assert(mem.eql(u8, "ab0123", caps_non_capturing_1.sliceAt(0).?));
debug.assert(caps_non_capturing_1.slots.len == 2);

var r_non_capturing_2 = try Regex.compile(std.testing.allocator, "(?:ab(cd))");
defer r_non_capturing_2.deinit();

var caps_non_capturing_2 = (try r_non_capturing_2.captures("xabcdx")).?;
defer caps_non_capturing_2.deinit();

debug.assert(mem.eql(u8, "abcd", caps_non_capturing_2.sliceAt(0).?));
debug.assert(mem.eql(u8, "cd", caps_non_capturing_2.sliceAt(1).?));
}

test "regex memory leaks" {
Expand Down