Merge #16887: Abstract out some of the descriptor Span-parsing helpers

bb36372b8f2bd675313ae8553ceb61f28c2c1afd test: add unit tests for Span-parsing helpers (Sebastian Falbesoner)
5e69aeec3f2a0fafd5e591b7222716f00145761d Add documenting comments to spanparsing.h (Pieter Wuille)
230d43fdbc41b356700b0d8a6984d69e00279ade Abstract out some of the descriptor Span-parsing helpers (Pieter Wuille)

Pull request description:

  As suggested here: https://github.com/bitcoin/bitcoin/pull/16800#issuecomment-531605482.

  This moves the Span parsing functions out of the descriptor module, making them more easily usable for other parsers (in particular, in preparation for miniscript parsing).

ACKs for top commit:
  MarcoFalke:
    ACK bb36372b8f2bd675313ae8553ceb61f28c2c1afd

Tree-SHA512: b5c5c11a9bc3f0a1c2c4cfa22755654ecfb8d4b69da0dc1fb9f04e1556dc0f6ffd87ad153600963279ac465d587d7971b53d240ced802d12693682411ac73deb

1 files changed, 124 insertions, 0 deletions

diff --git a/src/test/util_tests.cpp b/src/test/util_tests.cpp
index d0cd4b0a0..31a66b6fa 100644
--- a/src/test/util_tests.cpp
+++ b/src/test/util_tests.cpp
@@ -12,6 +12,7 @@
 #include <util/strencodings.h>
 #include <util/string.h>
 #include <util/time.h>
+#include <util/spanparsing.h>
 
 #include <stdint.h>
 #include <thread>
@@ -1572,4 +1573,127 @@ BOOST_AUTO_TEST_CASE(test_Capitalize)
     BOOST_CHECK_EQUAL(Capitalize("\x00\xfe\xff"), "\x00\xfe\xff");
 }
 
+static std::string SpanToStr(Span<const char>& span)
+{
+    return std::string(span.begin(), span.end());
+}
+
+BOOST_AUTO_TEST_CASE(test_spanparsing)
+{
+    using namespace spanparsing;
+    std::string input;
+    Span<const char> sp;
+    bool success;
+
+    // Const(...): parse a constant, update span to skip it if successful
+    input = "MilkToastHoney";
+    sp = MakeSpan(input);
+    success = Const("", sp); // empty
+    BOOST_CHECK(success);
+    BOOST_CHECK_EQUAL(SpanToStr(sp), "MilkToastHoney");
+
+    success = Const("Milk", sp);
+    BOOST_CHECK(success);
+    BOOST_CHECK_EQUAL(SpanToStr(sp), "ToastHoney");
+
+    success = Const("Bread", sp);
+    BOOST_CHECK(!success);
+
+    success = Const("Toast", sp);
+    BOOST_CHECK(success);
+    BOOST_CHECK_EQUAL(SpanToStr(sp), "Honey");
+
+    success = Const("Honeybadger", sp);
+    BOOST_CHECK(!success);
+
+    success = Const("Honey", sp);
+    BOOST_CHECK(success);
+    BOOST_CHECK_EQUAL(SpanToStr(sp), "");
+
+    // Func(...): parse a function call, update span to argument if successful
+    input = "Foo(Bar(xy,z()))";
+    sp = MakeSpan(input);
+
+    success = Func("FooBar", sp);
+    BOOST_CHECK(!success);
+
+    success = Func("Foo(", sp);
+    BOOST_CHECK(!success);
+
+    success = Func("Foo", sp);
+    BOOST_CHECK(success);
+    BOOST_CHECK_EQUAL(SpanToStr(sp), "Bar(xy,z())");
+
+    success = Func("Bar", sp);
+    BOOST_CHECK(success);
+    BOOST_CHECK_EQUAL(SpanToStr(sp), "xy,z()");
+
+    success = Func("xy", sp);
+    BOOST_CHECK(!success);
+
+    // Expr(...): return expression that span begins with, update span to skip it
+    Span<const char> result;
+
+    input = "(n*(n-1))/2";
+    sp = MakeSpan(input);
+    result = Expr(sp);
+    BOOST_CHECK_EQUAL(SpanToStr(result), "(n*(n-1))/2");
+    BOOST_CHECK_EQUAL(SpanToStr(sp), "");
+
+    input = "foo,bar";
+    sp = MakeSpan(input);
+    result = Expr(sp);
+    BOOST_CHECK_EQUAL(SpanToStr(result), "foo");
+    BOOST_CHECK_EQUAL(SpanToStr(sp), ",bar");
+
+    input = "(aaaaa,bbbbb()),c";
+    sp = MakeSpan(input);
+    result = Expr(sp);
+    BOOST_CHECK_EQUAL(SpanToStr(result), "(aaaaa,bbbbb())");
+    BOOST_CHECK_EQUAL(SpanToStr(sp), ",c");
+
+    input = "xyz)foo";
+    sp = MakeSpan(input);
+    result = Expr(sp);
+    BOOST_CHECK_EQUAL(SpanToStr(result), "xyz");
+    BOOST_CHECK_EQUAL(SpanToStr(sp), ")foo");
+
+    input = "((a),(b),(c)),xxx";
+    sp = MakeSpan(input);
+    result = Expr(sp);
+    BOOST_CHECK_EQUAL(SpanToStr(result), "((a),(b),(c))");
+    BOOST_CHECK_EQUAL(SpanToStr(sp), ",xxx");
+
+    // Split(...): split a string on every instance of sep, return vector
+    std::vector<Span<const char>> results;
+
+    input = "xxx";
+    results = Split(MakeSpan(input), 'x');
+    BOOST_CHECK_EQUAL(results.size(), 4);
+    BOOST_CHECK_EQUAL(SpanToStr(results[0]), "");
+    BOOST_CHECK_EQUAL(SpanToStr(results[1]), "");
+    BOOST_CHECK_EQUAL(SpanToStr(results[2]), "");
+    BOOST_CHECK_EQUAL(SpanToStr(results[3]), "");
+
+    input = "one#two#three";
+    results = Split(MakeSpan(input), '-');
+    BOOST_CHECK_EQUAL(results.size(), 1);
+    BOOST_CHECK_EQUAL(SpanToStr(results[0]), "one#two#three");
+
+    input = "one#two#three";
+    results = Split(MakeSpan(input), '#');
+    BOOST_CHECK_EQUAL(results.size(), 3);
+    BOOST_CHECK_EQUAL(SpanToStr(results[0]), "one");
+    BOOST_CHECK_EQUAL(SpanToStr(results[1]), "two");
+    BOOST_CHECK_EQUAL(SpanToStr(results[2]), "three");
+
+    input = "*foo*bar*";
+    results = Split(MakeSpan(input), '*');
+    BOOST_CHECK_EQUAL(results.size(), 4);
+    BOOST_CHECK_EQUAL(SpanToStr(results[0]), "");
+    BOOST_CHECK_EQUAL(SpanToStr(results[1]), "foo");
+    BOOST_CHECK_EQUAL(SpanToStr(results[2]), "bar");
+    BOOST_CHECK_EQUAL(SpanToStr(results[3]), "");
+}
+
 BOOST_AUTO_TEST_SUITE_END()