commit 7ecd39644988c390f44d0c92d700b285d27d46fb
Author: GRISHNOV <grishnov98@mail.ru>
Date:   Tue Nov 17 19:32:34 2020 +0300

    add main header file

diff --git a/include/PKCS7.h b/include/PKCS7.h
new file mode 100644
index 0000000..d5b74dd
--- /dev/null
+++ b/include/PKCS7.h
@@ -0,0 +1,49 @@
+#ifndef PKCS7_H
+#define PKCS7_H
+
+/* 
+    Examples of commonly used block sizes for data padding.
+    WARNING: block size for PKCS7 padding can be 0 < BLOCK_SIZE < 256 bytes.
+*/
+typedef enum {
+    BLOCK_SIZE_128_BIT      = 128 / 8,  /* 16 bytes block */
+    BLOCK_SIZE_256_BIT      = 256 / 8,  /* 32 bytes block */
+    BLOCK_SIZE_CUSTOM_VALUE = 0         /* you can set your own constant to use */
+} paddingBlockSize;                     /* can be used as third argument to the function addPadding() */
+
+
+/* 
+    A pointer to this structure is returned from the function addPadding().
+    The structure contains result of adding PKCS7 padding.
+*/
+typedef struct {
+    void*         dataWithPadding;          /* result of adding padding to the data */
+    unsigned char dataLengthWithPadding;    /* length of the result */
+    unsigned char valueOfByteForPadding;    /* used for padding byte value */
+} PKCS7_Padding;                            
+
+/* 
+    Applies PKCS7 padding to data.
+    Your data at the provided address does not change. A copy is created, to which the adding padding is applied.
+    WARNING: use only 0 < BLOCK_SIZE < 256
+*/
+PKCS7_Padding* addPadding(const void* const data, const unsigned int dataLength, const unsigned char BLOCK_SIZE);
+
+
+/* 
+    A pointer to this structure is returned from the function removePadding().
+    The structure contains result of removing PKCS7 padding.
+*/
+typedef struct {
+    void*         dataWithoutPadding;           /* result of remove padding from data */
+    unsigned char dataLengthWithoutPadding;     /* length of the result */
+    unsigned char valueOfRemovedByteFromData;   /* value of byte that was used for padding */
+} PKCS7_unPadding;                              
+
+/* 
+    Remove PKCS7 padding from data.
+    Your data at the provided address does not change. A copy is created, to which the removing padding is applied.
+*/
+PKCS7_unPadding* removePadding(const void* const data, const unsigned int dataLength);
+
+#endif // PKCS7_H
\ No newline at end of file