Move `shell_words` into its own file

Change-Id: I34c0ebfb6dcea49bf632d8880e04075335a132bf

1 files changed, 77 insertions, 0 deletions

diff --git a/src/libutil/shlex.cc b/src/libutil/shlex.cc
new file mode 100644
index 000000000..b5f340251
--- /dev/null
+++ b/src/libutil/shlex.cc
@@ -0,0 +1,77 @@
+#include "shlex.hh"
+#include "util.hh"
+
+namespace nix {
+
+std::vector<std::string> shell_split(const std::string & input)
+{
+    std::vector<std::string> result;
+
+    // Hack: `shell_split` is janky and parses ` a` as `{"", "a"}`, so we trim
+    // whitespace before starting.
+    auto inputTrimmed = trim(input);
+
+    if (inputTrimmed.empty()) {
+        return result;
+    }
+
+    std::regex whitespace("^\\s+");
+    auto begin = inputTrimmed.cbegin();
+    std::string currentToken;
+    enum State { sBegin, sSingleQuote, sDoubleQuote };
+    State state = sBegin;
+    auto iterator = begin;
+
+    for (; iterator != inputTrimmed.cend(); ++iterator) {
+        if (state == sBegin) {
+            std::smatch match;
+            if (regex_search(iterator, inputTrimmed.cend(), match, whitespace)) {
+                currentToken.append(begin, iterator);
+                result.push_back(currentToken);
+                iterator = match[0].second;
+                if (iterator == inputTrimmed.cend()) {
+                    return result;
+                }
+                begin = iterator;
+                currentToken.clear();
+            }
+        }
+
+        switch (*iterator) {
+        case '\'':
+            if (state != sDoubleQuote) {
+                currentToken.append(begin, iterator);
+                begin = iterator + 1;
+                state = state == sBegin ? sSingleQuote : sBegin;
+            }
+            break;
+
+        case '"':
+            if (state != sSingleQuote) {
+                currentToken.append(begin, iterator);
+                begin = iterator + 1;
+                state = state == sBegin ? sDoubleQuote : sBegin;
+            }
+            break;
+
+        case '\\':
+            if (state != sSingleQuote) {
+                // perl shellwords mostly just treats the next char as part
+                // of the string with no special processing
+                currentToken.append(begin, iterator);
+                begin = ++iterator;
+            }
+            break;
+        }
+    }
+
+    if (state != sBegin) {
+        throw ShlexError(input);
+    }
+
+    currentToken.append(begin, iterator);
+    result.push_back(currentToken);
+    return result;
+}
+
+}