[tarantool-patches] [PATCH] lua: Add string.decodehex method

["" <dmarc-noreply@freelists.org> (Redacted sender "gleb-skiba" for DMARC)]

From: Gleb <gleb-skiba@mail.ru>

Add string.fromhex method.
Add test for string.fromhex().

Fixes #2562
---
Issue from https://github.com/tarantool/tarantool/issues/2562.
Source from https://github.com/tarantool/tarantool/compare/gh-2562-string-bin?expand=1.
 src/lua/string.lua           | 30 ++++++++++++++++++++++++++++++
 test/app-tap/string.test.lua | 12 +++++++++++-
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/src/lua/string.lua b/src/lua/string.lua
index 5ff64c9..c2a7198 100644
--- a/src/lua/string.lua
+++ b/src/lua/string.lua
@@ -292,6 +292,35 @@ local function string_hex(inp)
     return ffi.string(res, len)
 end
 
+local tonum = {[48] = 0, [49] = 1, [50] = 2, [51] = 3, [52] = 4, [53] = 5,
+[54] = 6, [55] = 7, [56] = 8, [57] = 9, [97] = 10, [98] = 11,
+[99] = 12, [100] = 13, [101] = 14, [102] = 15, [65] = 10, [66] = 11,
+[67] = 12, [68] = 13, [69] = 14, [70] = 15 }
+
+local function string_fromhex(inp)
+    if type(inp) ~= 'string' then
+        error(err_string_arg:format(1, 'string.fromhex', 'string', type(inp)), 2)
+    end
+
+    if inp:len() % 2 ~= 0 then
+        error(err_string_arg:format(1, 'string.fromhex', 'even string', 'odd string'), 2)
+    end
+
+    local len = inp:len() / 2
+    local uinp = ffi.cast('const char *', inp)
+    local ans = ffi.new('char[?]', len)
+
+    for i = 0, len - 1 do
+        local first = tonum[uinp[i * 2]]
+        local second = tonum[uinp[i * 2 + 1]]
+        if ((first == nil) or (second == nil)) then
+            error(err_string_arg:format(1, 'string.fromhex', 'hex string', 'not hex string'), 2)
+        end
+        ans[i] = first * 16 + second
+    end
+    return ffi.string(ans, len)
+end
+
 local function string_strip(inp)
     if type(inp) ~= 'string' then
         error(err_string_arg:format(1, "string.strip", 'string', type(inp)), 2)
@@ -323,6 +352,7 @@ string.center     = string_center
 string.startswith = string_startswith
 string.endswith   = string_endswith
 string.hex        = string_hex
+string.fromhex    = string_fromhex
 string.strip      = string_strip
 string.lstrip      = string_lstrip
 string.rstrip      = string_rstrip
diff --git a/test/app-tap/string.test.lua b/test/app-tap/string.test.lua
index 852a792..685bb74 100755
--- a/test/app-tap/string.test.lua
+++ b/test/app-tap/string.test.lua
@@ -3,7 +3,7 @@
 local tap = require('tap')
 local test = tap.test("string extensions")
 
-test:plan(5)
+test:plan(6)
 
 test:test("split", function(test)
     test:plan(10)
@@ -114,6 +114,16 @@ test:test("hex", function(test)
     test:is(string.hex(""), "", "hex empty string")
 end)
 
+test:test("fromhex", function(test)
+    test:plan(4)
+    test:is(string.fromhex("48656c6c6f"), "Hello", "from hex to bin")
+    test:is(string.fromhex("4c696e7578"), "Linux", "from hex to bin")
+    local _, err = pcall(function() string.fromhex("aaa") end)
+    test:ok(err and err:match("(even string expected, got odd string)"), err)
+    _, err = pcall(function() string.fromhex("qq") end)
+    test:ok(err and err:match("(hex string expected, got not hex string)"), err)
+end)
+
 test:test("strip", function(test)
     test:plan(6)
     local str = "  hello hello "
-- 
2.7.4