Add stdint.readme for C90 compliance (#13)

Add a stdint.readme file to support toolchains that do not provide the stdint.h file for integer typedefs. With the provision of this file, the library can be used against C90 compilers. This PR also adds a CI check to ensure successful library builds when using the stdint.readme file for the standard C library header.

Author: aggarw13

.github/workflows/ci.yml

@@ -145,3 +145,17 @@ jobs:
         run: |
           git-secrets --register-aws
           git-secrets --scan
+  custom-standard-c-header:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Clone This Repo
+        uses: actions/checkout@v2
+      - name: Build
+        run: |
+          mkdir -p override-include
+          cp source/include/stdint.readme override-include/stdint.h
+          cmake -S test -B build/ \
+          -G "Unix Makefiles" \
+          -DBUILD_CLONE_SUBMODULES=ON \
+          -DCMAKE_C_FLAGS='-Wall -Wextra -Werror -I../override-include'
+          make -C build/ coverity_analysis

README.md

@@ -97,7 +97,10 @@ int main()
 
 ## Building the library
 
-A compiler that supports **C89 or later** such as *gcc* is required to build the library.
+A compiler that supports **C90 or later** such as *gcc* is required to build the library.
+
+Additionally, the library uses a header file introduced in ISO C99, `stdint.h`. For compilers that do not provide this header file, the [source/include](source/include) directory contains [stdint.readme](source/include/stdint.readme), which can be renamed to `stdint.h` to
+build the backoffAlgorithm library.
 
 For instance, if the example above is copied to a file named `example.c`, *gcc* can be used like so:
 ```bash

source/backoff_algorithm.c

@@ -27,8 +27,8 @@
  */
 
 /* Standard includes. */
-#include <stdlib.h>
 #include <assert.h>
+#include <stddef.h>
 
 /* Include API header. */
 #include "backoff_algorithm.h"

source/include/stdint.readme

@@ -0,0 +1,37 @@
+#ifndef _STDINT_H
+#define _STDINT_H
+
+/*******************************************************************************
+ * THIS IS NOT A FULL stdint.h IMPLEMENTATION - It only contains the definitions
+ * necessary to build the library code.  It is provided to allow the library to
+ * be built using compilers that do not provide their own stdint.h definition.
+ *
+ * To use this file:
+ *
+ *    1) Copy this file into a directory that is in your compiler's include path.
+ *       The directory must be part of the include path for system header file,
+ *       for example passed using gcc's "-I" or "-isystem" options.
+ *
+ *    2) Rename the copied file stdint.h.
+ *
+ */
+
+typedef signed char          int8_t;
+typedef unsigned char        uint8_t;
+typedef short                int16_t;
+typedef unsigned short       uint16_t;
+typedef long                 int32_t;
+typedef unsigned long        uint32_t;
+typedef long long            int64_t;
+typedef unsigned long long   uint64_t;
+
+#define INT8_MAX      ( ( signed char ) 127 )
+#define UINT8_MAX     ( ( unsigned char ) 255 )
+#define INT16_MAX     ( ( short ) 32767 )
+#define UINT16_MAX    ( ( unsigned short ) 65535 )
+#define INT32_MAX     2147483647L
+#define UINT32_MAX    4294967295UL
+#define INT64_MAX     9223372036854775807LL
+#define UINT64_MAX    18446744073709551615ULL
+
+#endif /* _STDINT_H */