Add CMake-based base64 port

4 years ago · b78bed90c5
parent 3618eabaf0
commit b78bed90c5
1 changed files with 74 additions and 0 deletions
--- a/cmake/base64.cmake
+++ b/cmake/base64.cmake
@ -0,0 +1,74 @@
+# math(EXPR "...") can't parse hex until 3.13
+cmake_minimum_required(VERSION 3.13)
+
+if (NOT DEFINED INPUT_FILE)
+    message(STATUS "Usage: cmake -DINPUT_FILE=\"infile.ext\" -DOUTPUT_FILE=\"out.txt\" -P base64.cmake")
+    message(FATAL_ERROR "INPUT_FILE not specified")
+endif()
+
+if (NOT DEFINED OUTPUT_FILE)
+    message(STATUS "Usage: cmake -DINPUT_FILE=\"infile.ext\" -DOUTPUT_FILE=\"out.txt\" -P base64.cmake")
+    message(FATAL_ERROR "OUTPUT_FILE not specified")
+endif()
+
+if (NOT EXISTS ${INPUT_FILE})
+    message(FATAL_ERROR "INPUT_FILE ${INPUT_FILE} does not exist")
+endif()
+
+set(lut "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/")
+
+file(READ "${INPUT_FILE}" hexContent HEX)
+
+set(base64Content "")
+while(TRUE)
+    string(LENGTH "${hexContent}" tailLength)
+    if (tailLength LESS 1)
+        break()
+    endif()
+
+    string(SUBSTRING "${hexContent}" 0 6 head)
+    # base64 works on three-byte chunks. Pad.
+    string(LENGTH "${head}" headLength)
+    if (headLength LESS 6)
+        set(hexContent "")
+        math(EXPR padSize "6 - ${headLength}")
+        set(pad "")
+        foreach(i RANGE 1 ${padSize})
+            string(APPEND pad "0")
+        endforeach()
+        string(APPEND head "${pad}")
+    else()
+        string(SUBSTRING "${hexContent}" 6 -1 hexContent)
+        set(padSize 0)   
+    endif()
+
+    # get six-bit slices
+    math(EXPR first "0x${head} >> 18")
+    math(EXPR second "(0x${head} & 0x3F000) >> 12")
+    math(EXPR third "(0x${head} & 0xFC0) >> 6")
+    math(EXPR fourth "0x${head} & 0x3F")
+
+    # first two characters are always needed to represent the first byte
+    string(SUBSTRING "${lut}" ${first} 1 char)
+    string(APPEND base64Content "${char}")
+    string(SUBSTRING "${lut}" ${second} 1 char)
+    string(APPEND base64Content "${char}")
+
+    # if there's no second byte, pad with =
+    if (NOT padSize EQUAL 4)
+        string(SUBSTRING "${lut}" ${third} 1 char)
+        string(APPEND base64Content "${char}")
+    else()
+        string(APPEND base64Content "=")
+    endif()
+
+    # if there's no third byte, pad with =
+    if (padSize EQUAL 0)
+        string(SUBSTRING "${lut}" ${fourth} 1 char)
+        string(APPEND base64Content "${char}")
+    else()
+        string(APPEND base64Content "=")
+    endif()
+endwhile()
+
+file(WRITE "${OUTPUT_FILE}" "${base64Content}")