Move /src to /subprojects

This will facilitate breaking up Nix into multiple packages for each
component with Meson.

subprojects/libutil/position.cc

@@ -0,0 +1,159 @@
+#include "position.hh"
+
+namespace nix {
+
+Pos::Pos(const Pos * other)
+{
+    if (!other) {
+        return;
+    }
+    line = other->line;
+    column = other->column;
+    origin = std::move(other->origin);
+}
+
+Pos::operator std::shared_ptr<Pos>() const
+{
+    return std::make_shared<Pos>(&*this);
+}
+
+std::optional<LinesOfCode> Pos::getCodeLines() const
+{
+    if (line == 0)
+        return std::nullopt;
+
+    if (auto source = getSource()) {
+        LinesIterator lines(*source), end;
+        LinesOfCode loc;
+
+        if (line > 1)
+            std::advance(lines, line - 2);
+        if (lines != end && line > 1)
+            loc.prevLineOfCode = *lines++;
+        if (lines != end)
+            loc.errLineOfCode = *lines++;
+        if (lines != end)
+            loc.nextLineOfCode = *lines++;
+
+        return loc;
+    }
+
+    return std::nullopt;
+}
+
+
+std::optional<std::string> Pos::getSource() const
+{
+    return std::visit(overloaded {
+        [](const std::monostate &) -> std::optional<std::string> {
+            return std::nullopt;
+        },
+        [](const Pos::Stdin & s) -> std::optional<std::string> {
+            // Get rid of the null terminators added by the parser.
+            return std::string(s.source->c_str());
+        },
+        [](const Pos::String & s) -> std::optional<std::string> {
+            // Get rid of the null terminators added by the parser.
+            return std::string(s.source->c_str());
+        },
+        [](const SourcePath & path) -> std::optional<std::string> {
+            try {
+                return path.readFile();
+            } catch (Error &) {
+                return std::nullopt;
+            }
+        }
+    }, origin);
+}
+
+void Pos::print(std::ostream & out, bool showOrigin) const
+{
+    if (showOrigin) {
+        std::visit(overloaded {
+            [&](const std::monostate &) { out << "«none»"; },
+            [&](const Pos::Stdin &) { out << "«stdin»"; },
+            [&](const Pos::String & s) { out << "«string»"; },
+            [&](const SourcePath & path) { out << path; }
+        }, origin);
+        out << ":";
+    }
+    out << line;
+    if (column > 0)
+        out << ":" << column;
+}
+
+std::ostream & operator<<(std::ostream & str, const Pos & pos)
+{
+    pos.print(str, true);
+    return str;
+}
+
+void Pos::LinesIterator::bump(bool atFirst)
+{
+    if (!atFirst) {
+        pastEnd = input.empty();
+        if (!input.empty() && input[0] == '\r')
+            input.remove_prefix(1);
+        if (!input.empty() && input[0] == '\n')
+            input.remove_prefix(1);
+    }
+
+    // nix line endings are not only \n as eg std::getline assumes, but also
+    // \r\n **and \r alone**. not treating them all the same causes error
+    // reports to not match with line numbers as the parser expects them.
+    auto eol = input.find_first_of("\r\n");
+
+    if (eol > input.size())
+        eol = input.size();
+
+    curLine = input.substr(0, eol);
+    input.remove_prefix(eol);
+}
+
+std::optional<std::string> Pos::getSnippetUpTo(const Pos & end) const {
+    assert(this->origin == end.origin);
+
+    if (end.line < this->line)
+        return std::nullopt;
+
+    if (auto source = getSource()) {
+
+        auto firstLine = LinesIterator(*source);
+        for (uint32_t i = 1; i < this->line; ++i) {
+            ++firstLine;
+        }
+
+        auto lastLine = LinesIterator(*source);
+        for (uint32_t i = 1; i < end.line; ++i) {
+            ++lastLine;
+        }
+
+        LinesIterator linesEnd;
+
+        std::string result;
+        for (auto i = firstLine; i != linesEnd; ++i) {
+            auto firstColumn = i == firstLine ? (this->column ? this->column - 1 : 0) : 0;
+            if (firstColumn > i->size())
+                firstColumn = i->size();
+
+            auto lastColumn = i == lastLine ? (end.column ? end.column - 1 : 0) : std::numeric_limits<int>::max();
+            if (lastColumn < firstColumn)
+                lastColumn = firstColumn;
+            if (lastColumn > i->size())
+                lastColumn = i->size();
+
+            result += i->substr(firstColumn, lastColumn - firstColumn);
+
+            if (i == lastLine) {
+                break;
+            } else {
+                result += '\n';
+            }
+        }
+        return result;
+    }
+    return std::nullopt;
+}
+
+
+}