feat(stdlib): add vim.base64 module (#25843)

Add base64 encode() and decode() functions to a vim.base64 module.

10 files changed, 448 insertions, 1 deletions

diff --git a/runtime/doc/lua.txt b/runtime/doc/lua.txt
index 1d69b1cc91..aea19d7bf0 100644
--- a/runtime/doc/lua.txt
+++ b/runtime/doc/lua.txt
@@ -810,6 +810,28 @@ vim.json.encode({obj})                                     *vim.json.encode()*
 
 
 ==============================================================================
+VIM.BASE64                                                        *vim.base64*
+
+vim.base64.decode({str})                                 *vim.base64.decode()*
+    Decode a Base64 encoded string.
+
+    Parameters: ~
+      • {str}  (string) Base64 encoded string
+
+    Return: ~
+        (string) Decoded string
+
+vim.base64.encode({str})                                 *vim.base64.encode()*
+    Encode {str} using Base64.
+
+    Parameters: ~
+      • {str}  (string) String to encode
+
+    Return: ~
+        (string) Encoded string
+
+
+==============================================================================
 VIM.SPELL                                                          *vim.spell*
 
 vim.spell.check({str})                                     *vim.spell.check()*
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index d1191bef9a..b88b7d164f 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -202,6 +202,9 @@ The following new APIs and features were added.
 
 • 'complete' option supports "f" flag for completing buffer names.
 
+• Added |vim.base64.encode()| and |vim.base64.decode()| for encoding and decoding
+  strings using Base64 encoding.
+
 ==============================================================================
 CHANGED FEATURES                                                 *news-changed*
 
diff --git a/runtime/lua/vim/_meta/base64.lua b/runtime/lua/vim/_meta/base64.lua
new file mode 100644
index 0000000000..f25b4af234
--- /dev/null
+++ b/runtime/lua/vim/_meta/base64.lua
@@ -0,0 +1,13 @@
+--- @meta
+
+--- Encode {str} using Base64.
+---
+--- @param str string String to encode
+--- @return string Encoded string
+function vim.base64.encode(str) end
+
+--- Decode a Base64 encoded string.
+---
+--- @param str string Base64 encoded string
+--- @return string Decoded string
+function vim.base64.decode(str) end
diff --git a/scripts/gen_vimdoc.py b/scripts/gen_vimdoc.py
index 13f64c44a3..1f10a39e35 100755
--- a/scripts/gen_vimdoc.py
+++ b/scripts/gen_vimdoc.py
@@ -150,6 +150,7 @@ CONFIG = {
             'diff.lua',
             'mpack.lua',
             'json.lua',
+            'base64.lua',
             'spell.lua',
             'builtin.lua',
             '_options.lua',
@@ -187,6 +188,7 @@ CONFIG = {
             'runtime/lua/vim/_meta/diff.lua',
             'runtime/lua/vim/_meta/mpack.lua',
             'runtime/lua/vim/_meta/json.lua',
+            'runtime/lua/vim/_meta/base64.lua',
             'runtime/lua/vim/_meta/regex.lua',
             'runtime/lua/vim/_meta/spell.lua',
         ],
@@ -206,7 +208,7 @@ CONFIG = {
         'section_fmt': lambda name: (
             'Lua module: vim' if name.lower() == '_editor' else
             'LUA-VIMSCRIPT BRIDGE' if name.lower() == '_options' else
-            f'VIM.{name.upper()}' if name.lower() in [ 'highlight', 'mpack', 'json', 'diff', 'spell', 'regex' ] else
+            f'VIM.{name.upper()}' if name.lower() in [ 'highlight', 'mpack', 'json', 'base64', 'diff', 'spell', 'regex' ] else
             'VIM' if name.lower() == 'builtin' else
             f'Lua module: vim.{name.lower()}'),
         'helptag_fmt': lambda name: (
@@ -241,6 +243,7 @@ CONFIG = {
             'builtin': 'vim',
             'mpack': 'vim.mpack',
             'json': 'vim.json',
+            'base64': 'vim.base64',
             'regex': 'vim.regex',
             'spell': 'vim.spell',
         },
diff --git a/src/nvim/base64.c b/src/nvim/base64.c
new file mode 100644
index 0000000000..95aa491281
--- /dev/null
+++ b/src/nvim/base64.c
@@ -0,0 +1,209 @@
+#include <assert.h>
+#include <stddef.h>
+#include <string.h>
+
+#include "nvim/base64.h"
+#include "nvim/memory.h"
+
+#ifdef HAVE_BE64TOH
+# include ENDIAN_INCLUDE_FILE
+#endif
+
+static const char alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+// Indices are 1-based because we use 0 to indicate a letter that is not part of the alphabet
+static const uint8_t char_to_index[256] = {
+  ['A'] = 1,  ['B'] = 2,  ['C'] = 3, ['D'] = 4,  ['E'] = 5,  ['F'] = 6,  ['G'] = 7,  ['H'] = 8,
+  ['I'] = 9,  ['J'] = 10, ['K'] = 11, ['L'] = 12, ['M'] = 13, ['N'] = 14, ['O'] = 15, ['P'] = 16,
+  ['Q'] = 17, ['R'] = 18, ['S'] = 19, ['T'] = 20, ['U'] = 21, ['V'] = 22, ['W'] = 23, ['X'] = 24,
+  ['Y'] = 25, ['Z'] = 26, ['a'] = 27, ['b'] = 28, ['c'] = 29, ['d'] = 30, ['e'] = 31, ['f'] = 32,
+  ['g'] = 33, ['h'] = 34, ['i'] = 35, ['j'] = 36, ['k'] = 37, ['l'] = 38, ['m'] = 39, ['n'] = 40,
+  ['o'] = 41, ['p'] = 42, ['q'] = 43, ['r'] = 44, ['s'] = 45, ['t'] = 46, ['u'] = 47, ['v'] = 48,
+  ['w'] = 49, ['x'] = 50, ['y'] = 51, ['z'] = 52, ['0'] = 53, ['1'] = 54, ['2'] = 55, ['3'] = 56,
+  ['4'] = 57, ['5'] = 58, ['6'] = 59, ['7'] = 60, ['8'] = 61, ['9'] = 62, ['+'] = 63, ['/'] = 64,
+};
+
+#ifndef HAVE_BE64TOH
+static inline uint64_t htobe64(uint64_t host_64bits)
+{
+# ifdef ORDER_BIG_ENDIAN
+  return host_64bits;
+# else
+  uint8_t *buf = (uint8_t *)&host_64bits;
+  uint64_t ret = 0;
+  for (size_t i = 8; i; i--) {
+    ret |= ((uint64_t)buf[i - 1]) << ((8 - i) * 8);
+  }
+  return ret;
+# endif
+}
+
+static inline uint32_t htobe32(uint32_t host_32bits)
+{
+# ifdef ORDER_BIG_ENDIAN
+  return host_32bits;
+# else
+  uint8_t *buf = (uint8_t *)&host_32bits;
+  uint32_t ret = 0;
+  for (size_t i = 4; i; i--) {
+    ret |= ((uint32_t)buf[i - 1]) << ((4 - i) * 8);
+  }
+  return ret;
+# endif
+}
+#endif
+
+/// Encode a string using Base64.
+///
+/// @param src String to encode
+/// @param src_len Length of the string
+/// @return Base64 encoded string
+char *base64_encode(const char *src, size_t src_len)
+{
+  assert(src != NULL);
+
+  const size_t out_len = ((src_len + 2) / 3) * 4;
+  char *dest = xmalloc(out_len + 1);
+
+  size_t src_i = 0;
+  size_t out_i = 0;
+
+  const uint8_t *s = (const uint8_t *)src;
+
+  // Read 8 bytes at a time as much as we can
+  for (; src_i + 7 < src_len; src_i += 6) {
+    uint64_t bits_h;
+    memcpy(&bits_h, &s[src_i], sizeof(uint64_t));
+    const uint64_t bits_be = htobe64(bits_h);
+    dest[out_i + 0] = alphabet[(bits_be >> 58) & 0x3F];
+    dest[out_i + 1] = alphabet[(bits_be >> 52) & 0x3F];
+    dest[out_i + 2] = alphabet[(bits_be >> 46) & 0x3F];
+    dest[out_i + 3] = alphabet[(bits_be >> 40) & 0x3F];
+    dest[out_i + 4] = alphabet[(bits_be >> 34) & 0x3F];
+    dest[out_i + 5] = alphabet[(bits_be >> 28) & 0x3F];
+    dest[out_i + 6] = alphabet[(bits_be >> 22) & 0x3F];
+    dest[out_i + 7] = alphabet[(bits_be >> 16) & 0x3F];
+    out_i += sizeof(uint64_t);
+  }
+
+  for (; src_i + 3 < src_len; src_i += 3) {
+    uint32_t bits_h;
+    memcpy(&bits_h, &s[src_i], sizeof(uint32_t));
+    const uint32_t bits_be = htobe32(bits_h);
+    dest[out_i + 0] = alphabet[(bits_be >> 26) & 0x3F];
+    dest[out_i + 1] = alphabet[(bits_be >> 20) & 0x3F];
+    dest[out_i + 2] = alphabet[(bits_be >> 14) & 0x3F];
+    dest[out_i + 3] = alphabet[(bits_be >> 8) & 0x3F];
+    out_i += sizeof(uint32_t);
+  }
+
+  if (src_i + 2 < src_len) {
+    dest[out_i + 0] = alphabet[s[src_i] >> 2];
+    dest[out_i + 1] = alphabet[((s[src_i] & 0x3) << 4) | (s[src_i + 1] >> 4)];
+    dest[out_i + 2] = alphabet[(s[src_i + 1] & 0xF) << 2 | (s[src_i + 2] >> 6)];
+    dest[out_i + 3] = alphabet[(s[src_i + 2] & 0x3F)];
+    out_i += 4;
+  } else if (src_i + 1 < src_len) {
+    dest[out_i + 0] = alphabet[s[src_i] >> 2];
+    dest[out_i + 1] = alphabet[((s[src_i] & 0x3) << 4) | (s[src_i + 1] >> 4)];
+    dest[out_i + 2] = alphabet[(s[src_i + 1] & 0xF) << 2];
+    out_i += 3;
+  } else if (src_i < src_len) {
+    dest[out_i + 0] = alphabet[s[src_i] >> 2];
+    dest[out_i + 1] = alphabet[(s[src_i] & 0x3) << 4];
+    out_i += 2;
+  }
+
+  for (; out_i < out_len; out_i++) {
+    dest[out_i] = '=';
+  }
+
+  dest[out_len] = '\0';
+
+  return dest;
+}
+
+/// Decode a Base64 encoded string.
+///
+/// @param src Base64 encoded string
+/// @param src_len Length of {src}
+/// @return Decoded string
+char *base64_decode(const char *src, size_t src_len)
+{
+  assert(src != NULL);
+
+  char *dest = NULL;
+
+  if (src_len % 4 != 0) {
+    goto invalid;
+  }
+
+  size_t out_len = (src_len / 4) * 3;
+  if (src_len >= 1 && src[src_len - 1] == '=') {
+    out_len--;
+  }
+  if (src_len >= 2 && src[src_len - 2] == '=') {
+    out_len--;
+  }
+
+  const uint8_t *s = (const uint8_t *)src;
+
+  dest = xmalloc(out_len + 1);
+
+  int acc = 0;
+  int acc_len = 0;
+  size_t out_i = 0;
+  size_t src_i = 0;
+  int leftover_i = -1;
+
+  for (; src_i < src_len; src_i++) {
+    const uint8_t c = s[src_i];
+    const uint8_t d = char_to_index[c];
+    if (d == 0) {
+      if (c == '=') {
+        leftover_i = (int)src_i;
+        break;
+      }
+      goto invalid;
+    }
+
+    acc = ((acc << 6) & 0xFFF) + (d - 1);
+    acc_len += 6;
+    if (acc_len >= 8) {
+      acc_len -= 8;
+      dest[out_i] = (char)(acc >> acc_len);
+      out_i += 1;
+    }
+  }
+
+  if (acc_len > 4 || ((acc & ((1 << acc_len) - 1)) != 0)) {
+    goto invalid;
+  }
+
+  if (leftover_i >= -1) {
+    int padding_len = acc_len / 2;
+    int padding_chars = 0;
+    for (; (size_t)leftover_i < src_len; leftover_i++) {
+      const uint8_t c = s[leftover_i];
+      if (c != '=') {
+        goto invalid;
+      }
+      padding_chars += 1;
+    }
+
+    if (padding_chars != padding_len) {
+      goto invalid;
+    }
+  }
+
+  dest[out_len] = '\0';
+
+  return dest;
+
+invalid:
+  if (dest) {
+    xfree((void *)dest);
+  }
+
+  return NULL;
+}
diff --git a/src/nvim/base64.h b/src/nvim/base64.h
new file mode 100644
index 0000000000..2162fd9ba2
--- /dev/null
+++ b/src/nvim/base64.h
@@ -0,0 +1,10 @@
+#ifndef NVIM_BASE64_H
+#define NVIM_BASE64_H
+
+#include <stddef.h>
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "base64.h.generated.h"
+#endif
+
+#endif  // NVIM_BASE64_H
diff --git a/src/nvim/lua/base64.c b/src/nvim/lua/base64.c
new file mode 100644
index 0000000000..3f246839d5
--- /dev/null
+++ b/src/nvim/lua/base64.c
@@ -0,0 +1,65 @@
+#include <assert.h>
+#include <lauxlib.h>
+#include <lua.h>
+
+#include "nvim/base64.h"
+#include "nvim/lua/base64.h"
+#include "nvim/memory.h"
+
+static int nlua_base64_encode(lua_State *L)
+{
+  if (lua_gettop(L) < 1) {
+    return luaL_error(L, "Expected 1 argument");
+  }
+
+  if (lua_type(L, 1) != LUA_TSTRING) {
+    luaL_argerror(L, 1, "expected string");
+  }
+
+  size_t src_len = 0;
+  const char *src = lua_tolstring(L, 1, &src_len);
+
+  const char *ret = base64_encode(src, src_len);
+  assert(ret != NULL);
+  lua_pushstring(L, ret);
+  xfree((void *)ret);
+
+  return 1;
+}
+
+static int nlua_base64_decode(lua_State *L)
+{
+  if (lua_gettop(L) < 1) {
+    return luaL_error(L, "Expected 1 argument");
+  }
+
+  if (lua_type(L, 1) != LUA_TSTRING) {
+    luaL_argerror(L, 1, "expected string");
+  }
+
+  size_t src_len = 0;
+  const char *src = lua_tolstring(L, 1, &src_len);
+
+  const char *ret = base64_decode(src, src_len);
+  if (ret == NULL) {
+    return luaL_error(L, "Invalid input");
+  }
+
+  lua_pushstring(L, ret);
+  xfree((void *)ret);
+
+  return 1;
+}
+
+static const luaL_Reg base64_functions[] = {
+  { "encode", nlua_base64_encode },
+  { "decode", nlua_base64_decode },
+  { NULL, NULL },
+};
+
+int luaopen_base64(lua_State *L)
+{
+  lua_newtable(L);
+  luaL_register(L, NULL, base64_functions);
+  return 1;
+}
diff --git a/src/nvim/lua/base64.h b/src/nvim/lua/base64.h
new file mode 100644
index 0000000000..570d9eb677
--- /dev/null
+++ b/src/nvim/lua/base64.h
@@ -0,0 +1,12 @@
+#ifndef NVIM_LUA_BASE64_H
+#define NVIM_LUA_BASE64_H
+
+#include <lauxlib.h>
+#include <lua.h>
+#include <lualib.h>
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "lua/base64.h.generated.h"
+#endif
+
+#endif  // NVIM_LUA_BASE64_H
diff --git a/src/nvim/lua/stdlib.c b/src/nvim/lua/stdlib.c
index 14e9902ee2..60be771b6c 100644
--- a/src/nvim/lua/stdlib.c
+++ b/src/nvim/lua/stdlib.c
@@ -26,6 +26,7 @@
 #include "nvim/ex_eval.h"
 #include "nvim/fold.h"
 #include "nvim/globals.h"
+#include "nvim/lua/base64.h"
 #include "nvim/lua/converter.h"
 #include "nvim/lua/spell.h"
 #include "nvim/lua/stdlib.h"
@@ -606,6 +607,10 @@ void nlua_state_add_stdlib(lua_State *const lstate, bool is_thread)
     lua_pushcfunction(lstate, &nlua_iconv);
     lua_setfield(lstate, -2, "iconv");
 
+    // vim.base64
+    luaopen_base64(lstate);
+    lua_setfield(lstate, -2, "base64");
+
     nlua_state_add_internal(lstate);
   }
 
diff --git a/test/functional/lua/base64_spec.lua b/test/functional/lua/base64_spec.lua
new file mode 100644
index 0000000000..f0d112c23e
--- /dev/null
+++ b/test/functional/lua/base64_spec.lua
@@ -0,0 +1,105 @@
+local helpers = require('test.functional.helpers')(after_each)
+local clear = helpers.clear
+local exec_lua = helpers.exec_lua
+local eq = helpers.eq
+local pcall_err = helpers.pcall_err
+local matches = helpers.matches
+
+describe('vim.base64', function()
+  before_each(clear)
+
+  local function encode(s)
+    return exec_lua([[return vim.base64.encode(...)]], s)
+  end
+
+  local function decode(s)
+    return exec_lua([[return vim.base64.decode(...)]], s)
+  end
+
+  it('works', function()
+    local values = {
+      '',
+      'Many hands make light work.',
+      [[
+        Call me Ishmael. Some years ago—never mind how long precisely—having little or no money in
+        my purse, and nothing particular to interest me on shore, I thought I would sail about a
+        little and see the watery part of the world.
+      ]],
+      [[
+        It is a truth universally acknowledged, that a single man in possession of a good fortune,
+        must be in want of a wife.
+      ]],
+      'Happy families are all alike; every unhappy family is unhappy in its own way.',
+      'ЁЂЃЄЅІЇЈЉЊЋЌЍЎЏАБВГДЕЖЗИЙКЛМНОПРСТУФХЦЧШЩЪЫЬЭЮЯабвгдежзийклмнопрстуфхцчшщъыьэюя',
+      'ÅÍÎÏ˝ÓÔÒÚÆ☃',
+      '𐐜 𐐔𐐇𐐝𐐀𐐡𐐇𐐓 𐐙𐐊𐐡𐐝𐐓/𐐝𐐇𐐗𐐊𐐤𐐔 𐐒𐐋𐐗 𐐒𐐌 𐐜 𐐡𐐀𐐖𐐇𐐤𐐓𐐝 𐐱𐑂 𐑄 𐐔𐐇𐐝𐐀𐐡𐐇𐐓 𐐏𐐆𐐅𐐤𐐆𐐚𐐊𐐡𐐝𐐆𐐓𐐆',
+      '👨‍👩‍👦 👨‍👩‍👧‍👦 👨‍👨‍👦 👩‍👩‍👧 👨‍👦 👨‍👧‍👦 👩‍👦 👩‍👧‍👦',
+      'مُنَاقَشَةُ سُبُلِ اِسْتِخْدَامِ اللُّغَةِ فِي النُّظُمِ الْقَائِمَةِ وَفِيم يَخُصَّ التَّطْبِيقَاتُ الْحاسُوبِيَّةُ،',
+      [[
+        Ṱ̺̺̕o͞ ̷i̲̬͇̪͙n̝̗͕v̟̜̘̦͟o̶̙̰̠kè͚̮̺̪̹̱̤ ̖t̝͕̳̣̻̪͞h̼͓̲̦̳̘̲e͇̣̰̦̬͎ ̢̼̻̱̘h͚͎͙̜̣̲ͅi̦̲̣̰̤v̻͍e̺̭̳̪̰-m̢iͅn̖̺̞̲̯̰d̵̼̟͙̩̼̘̳ ̞̥̱̳̭r̛̗̘e͙p͠r̼̞̻̭̗e̺̠̣͟s̘͇̳͍̝͉e͉̥̯̞̲͚̬͜ǹ̬͎͎̟̖͇̤t͍̬̤͓̼̭͘ͅi̪̱n͠g̴͉ ͏͉ͅc̬̟h͡a̫̻̯͘o̫̟̖͍̙̝͉s̗̦̲.̨̹͈̣
+        ̡͓̞ͅI̗̘̦͝n͇͇͙v̮̫ok̲̫̙͈i̖͙̭̹̠̞n̡̻̮̣̺g̲͈͙̭͙̬͎ ̰t͔̦h̞̲e̢̤ ͍̬̲͖f̴̘͕̣è͖ẹ̥̩l͖͔͚i͓͚̦͠n͖͍̗͓̳̮g͍ ̨o͚̪͡f̘̣̬ ̖̘͖̟͙̮c҉͔̫͖͓͇͖ͅh̵̤̣͚͔á̗̼͕ͅo̼̣̥s̱͈̺̖̦̻͢.̛̖̞̠̫̰
+        ̗̺͖̹̯͓Ṯ̤͍̥͇͈h̲́e͏͓̼̗̙̼̣͔ ͇̜̱̠͓͍ͅN͕͠e̗̱z̘̝̜̺͙p̤̺̹͍̯͚e̠̻̠͜r̨̤͍̺̖͔̖̖d̠̟̭̬̝͟i̦͖̩͓͔̤a̠̗̬͉̙n͚͜ ̻̞̰͚ͅh̵͉i̳̞v̢͇ḙ͎͟-҉̭̩̼͔m̤̭̫i͕͇̝̦n̗͙ḍ̟ ̯̲͕͞ǫ̟̯̰̲͙̻̝f ̪̰̰̗̖̭̘͘c̦͍̲̞͍̩̙ḥ͚a̮͎̟̙͜ơ̩̹͎s̤.̝̝ ҉Z̡̖̜͖̰̣͉̜a͖̰͙̬͡l̲̫̳͍̩g̡̟̼̱͚̞̬ͅo̗͜.̟
+        ̦H̬̤̗̤͝e͜ ̜̥̝̻͍̟́w̕h̖̯͓o̝͙̖͎̱̮ ҉̺̙̞̟͈W̷̼̭a̺̪͍į͈͕̭͙̯̜t̶̼̮s̘͙͖̕ ̠̫̠B̻͍͙͉̳ͅe̵h̵̬͇̫͙i̹͓̳̳̮͎̫̕n͟d̴̪̜̖ ̰͉̩͇͙̲͞ͅT͖̼͓̪͢h͏͓̮̻e̬̝̟ͅ ̤̹̝W͙̞̝͔͇͝ͅa͏͓͔̹̼̣l̴͔̰̤̟͔ḽ̫.͕
+        Z̮̞̠͙͔ͅḀ̗̞͈̻̗Ḷ͙͎̯̹̞͓G̻O̭̗̮
+      ]],
+    }
+
+    for _, v in ipairs(values) do
+      eq(v, decode(encode(v)))
+    end
+
+    -- Explicitly check encoded output
+    eq('VGhlIHF1aWNrIGJyb3duIGZveCBqdW1wcyBvdmVyIHRoZSBsYXp5IGRvZwo=', encode('The quick brown fox jumps over the lazy dog\n'))
+
+    -- Test vectors from rfc4648
+    local rfc4648 = {
+      { '', '' },
+      { 'f', 'Zg==', },
+      { 'fo', 'Zm8=' },
+      { 'foo', 'Zm9v' },
+      { 'foob', 'Zm9vYg==' },
+      { 'fooba', 'Zm9vYmE=' },
+      { 'foobar', 'Zm9vYmFy' },
+    }
+
+    for _, v in ipairs(rfc4648) do
+      local input = v[1]
+      local output = v[2]
+      eq(output, encode(input))
+      eq(input, decode(output))
+    end
+  end)
+
+  it('detects invalid input', function()
+    local invalid = {
+      'A',
+      'AA',
+      'AAA',
+      'A..A',
+      'AA=A',
+      'AA/=',
+      'A/==',
+      'A===',
+      '====',
+      'Zm9vYmFyZm9vYmFyA..A',
+      'Zm9vYmFyZm9vYmFyAA=A',
+      'Zm9vYmFyZm9vYmFyAA/=',
+      'Zm9vYmFyZm9vYmFyA/==',
+      'Zm9vYmFyZm9vYmFyA===',
+      'A..AZm9vYmFyZm9vYmFy',
+      'Zm9vYmFyZm9vAA=A',
+      'Zm9vYmFyZm9vAA/=',
+      'Zm9vYmFyZm9vA/==',
+      'Zm9vYmFyZm9vA===',
+    }
+
+    for _, v in ipairs(invalid) do
+      eq('Invalid input', pcall_err(decode, v))
+    end
+
+    eq('Expected 1 argument', pcall_err(encode))
+    eq('Expected 1 argument', pcall_err(decode))
+    matches('expected string', pcall_err(encode, 42))
+    matches('expected string', pcall_err(decode, 42))
+  end)
+end)