factor out SExpr/SExprWriter classes out of smtlib backend, and also tidy them up/document them

2025-06-19 20:33:39 +00:00 · 2024-07-11 11:30:23 +01:00 · 2024-07-11 11:30:23 +01:00 · 00a65754bb
commit 00a65754bb
parent c659ef29f4
4 changed files with 290 additions and 161 deletions
--- a/kernel/sexpr.cc
+++ b/kernel/sexpr.cc
@ -0,0 +1,163 @@
+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2024  Emily Schmidt <emily@yosyshq.com>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include "sexpr.h"
+
+YOSYS_NAMESPACE_BEGIN
+
+std::ostream &operator<<(std::ostream &os, SExpr const &sexpr) {
+    if(sexpr.is_atom())
+        os << sexpr.atom();
+    else if(sexpr.is_list()){
+        os << "(";
+        auto l = sexpr.list();
+        for(size_t i = 0; i < l.size(); i++) {
+            if(i > 0) os << " ";
+            os << l[i];
+        }
+        os << ")";
+    }else
+        os << "<invalid>";
+    return os;
+}
+
+ std::string SExpr::to_string() const {
+    std::stringstream ss;
+    ss << *this;
+    return ss.str();
+}
+
+void SExprWriter::nl_if_pending() {
+    if(_pending_nl) {
+        os << '\n';
+        _pos = 0;
+        _pending_nl = false;
+    }
+}
+
+void SExprWriter::puts(std::string_view s) {
+    if(s.empty()) return;
+    nl_if_pending();
+    for(auto c : s) {
+        if(c == '\n') {
+            os << c;
+            _pos = 0;
+        } else {
+            if(_pos == 0) {
+                for(int i = 0; i < _indent; i++)
+                    os << "  ";
+                _pos = 2 * _indent;
+            }
+            os << c;
+            _pos++;
+        }
+    }
+}
+
+
+// Calculate how much space would be left if expression was written
+// out in full horizontally. Returns any negative value if it doesn't fit.
+//
+// (Ideally we would avoid recalculating the widths of subexpression,
+// but I can't figure out how to store the widths. As an alternative,
+// we bail out of the calculation as soon as we can tell the expression
+// doesn't fit in the available space.)
+int SExprWriter::check_fit(SExpr const &sexpr, int space) {
+    if(sexpr.is_atom())
+        return space - sexpr.atom().size();
+    else if(sexpr.is_list()) {
+        space -= 2;
+        if(sexpr.list().size() > 1)
+            space -= sexpr.list().size() - 1;
+        for(auto arg : sexpr.list()) {
+            if(space < 0) break;
+            space = check_fit(arg, space);
+        }
+        return space;
+    } else
+        return -1;
+}
+
+void SExprWriter::print(SExpr const &sexpr, bool close, bool indent_rest) {
+    if(sexpr.is_atom())
+        puts(sexpr.atom());
+    else if(sexpr.is_list()) {
+        auto args = sexpr.list();
+        puts("(");
+        // Expressions are printed horizontally if they fit on the line.
+        // We do the check *after* puts("(") to make sure that _pos is accurate.
+        // (Otherwise there could be a pending newline + indentation)
+        bool vertical = args.size() > 1 && check_fit(sexpr, _max_line_width - _pos + 1) < 0;
+        if(vertical) _indent++;
+        for(size_t i = 0; i < args.size(); i++) {
+            if(i > 0) puts(vertical ? "\n" : " ");
+            print(args[i]);
+        }
+        // Any remaining arguments are currently always printed vertically,
+        // but are not indented if indent_rest = false.
+        _indent += (!close && indent_rest) - vertical;
+        if(close)
+            puts(")");
+        else {
+            _unclosed.push_back(indent_rest);
+            _pending_nl = true;
+        }
+    }else
+        log_error("shouldn't happen: SExpr '%s' is neither an atom nor a list", sexpr.to_string().c_str());
+}
+
+void SExprWriter::close(size_t n) {
+    log_assert(_unclosed.size() - (_unclosed_stack.empty() ? 0 : _unclosed_stack.back()) >= n);
+    while(n-- > 0) {
+        bool indented = _unclosed[_unclosed.size() - 1];
+        _unclosed.pop_back();
+        // Only print ) on the same line if it fits.
+        _pending_nl = _pos >= _max_line_width;
+        if(indented)
+            _indent--;
+        puts(")");
+        _pending_nl = true;
+    }
+}
+
+void SExprWriter::comment(std::string const &str, bool hanging) {
+    if(hanging) {
+        if(_pending_nl) {
+            _pending_nl = false;
+            puts(" ");
+        }
+    }
+    size_t i = 0, e;
+    do{
+        e = str.find('\n', i);
+        puts("; ");
+        puts(std::string_view(str).substr(i, e - i));
+        puts("\n");
+        i = e + 1;
+    }while(e != std::string::npos);
+}
+
+SExprWriter::~SExprWriter() {
+    while(!_unclosed_stack.empty())
+        pop();
+    close(_unclosed.size());
+    nl_if_pending();
+}
+
+YOSYS_NAMESPACE_END