From af4a6494a763493b2542ad9eb6f0c1807df49b0b Mon Sep 17 00:00:00 2001
From: JacobBarthelmeh <jacob@wolfssl.com>
Date: Tue, 6 Aug 2024 16:34:35 -0600
Subject: [PATCH] add size calculation example for static memory

---
 staticmemory/Makefile           | 43 +++++++++++++++++
 staticmemory/README.md          |  9 ++++
 staticmemory/size-calculation.c | 86 +++++++++++++++++++++++++++++++++
 3 files changed, 138 insertions(+)
 create mode 100644 staticmemory/Makefile
 create mode 100644 staticmemory/README.md
 create mode 100644 staticmemory/size-calculation.c

diff --git a/staticmemory/Makefile b/staticmemory/Makefile
new file mode 100644
index 00000000..bb3cd53c
--- /dev/null
+++ b/staticmemory/Makefile
@@ -0,0 +1,43 @@
+# ECC Examples Makefile
+CC       = gcc
+WOLFSSL_INSTALL_DIR = /usr/local
+CFLAGS   = -Wall -I$(WOLFSSL_INSTALL_DIR)/include
+ZLIB     =
+#ZLIB    += -lz
+LIBS     = -L$(WOLFSSL_INSTALL_DIR)/lib -lm ${ZLIB}
+
+# option variables
+DYN_LIB         = -lwolfssl
+STATIC_LIB      = $(WOLFSSL_INSTALL_DIR)/lib/libwolfssl.a
+DEBUG_FLAGS     = -g -DDEBUG
+DEBUG_INC_PATHS = -MD
+OPTIMIZE        = -Os
+
+# Options
+#CFLAGS+=$(DEBUG_FLAGS)
+CFLAGS+=$(OPTIMIZE)
+#LIBS+=$(STATIC_LIB)
+LIBS+=$(DYN_LIB)
+
+ifneq ($(PSA),)
+LIBS+=$(PSA_LIB)
+CFLAGS+=-DUSE_PSA
+endif
+
+# build targets
+SRC=$(wildcard *.c)
+TARGETS=$(patsubst %.c, %, $(SRC))
+
+.PHONY: clean all
+
+all: $(TARGETS)
+
+debug: CFLAGS+=$(DEBUG_FLAGS)
+debug: all
+
+# build template
+%: %.c
+	$(CC) -o $@ $< $(CFLAGS) $(LIBS)
+
+clean:
+	rm -f $(TARGETS)
diff --git a/staticmemory/README.md b/staticmemory/README.md
new file mode 100644
index 00000000..b5efb096
--- /dev/null
+++ b/staticmemory/README.md
@@ -0,0 +1,9 @@
+Examples of using wolfSSL's simple memory allocator. Enabled with --enable-staticmemory
+or WOLFSSL_STATIC_MEMORY when building wolfSSL. This is not a feature to reduce
+memory size!! It in fact uses a little more memory overhead. The staticmemory
+feature is used to have a simple fixed pool of memory available instead of using
+a systems malloc/free calls. Helpful in cases where dynamic memory is not
+allowed.
+
+wolfSSL has support for XMALLOC_USER which could be used to instead map XMALLOC
+and XFREE to any desired implementation of malloc/free.
diff --git a/staticmemory/size-calculation.c b/staticmemory/size-calculation.c
new file mode 100644
index 00000000..2762de97
--- /dev/null
+++ b/staticmemory/size-calculation.c
@@ -0,0 +1,86 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <wolfssl/options.h>
+#include <wolfssl/wolfcrypt/wc_port.h>
+#include <wolfssl/wolfcrypt/memory.h>
+
+#ifndef WOLFSSL_STATIC_MEMORY
+    #error requires --enable-staticmemory
+#endif
+
+int main(int argc, char** argv)
+{
+    int padSz;
+    const unsigned int dist[4] = {1, 1, 2, 1};
+    const unsigned int buck[4] = {10, 15, 20, 25};
+    byte* buf;
+    byte* testPtr[5];
+    int   buckTotalMem = 0; /* sum of bucket sizes */
+    int   totalMem;         /* sum of buckets and padding */
+    int   totalMemAll;      /* sum of buckets, padding, and managing structs */
+    int   i, k = 0;
+    WOLFSSL_HEAP_HINT* heapHint = NULL;
+
+    wolfCrypt_Init();
+
+    /* get padding size per bucket */
+    padSz = wolfSSL_MemoryPaddingSz();
+    printf("Padding size per bucket is %d\n", padSz);
+
+    /* calculate total size needed for individual bucket structs */
+    padSz = padSz * 5;
+    printf("Total padding needed for 5 buckets would be %d\n", padSz);
+
+    /* sum of all bucket sizes */
+    buckTotalMem = buck[0] + buck[1] + buck[2] + buck[2] + buck[3];
+    printf("Total memory in buckets is %d\n", buckTotalMem);
+
+    /* adding sum of bucket sizes with struct padding size */
+    totalMem = buckTotalMem + padSz;
+    printf("Calculated total memory for buckets is %d\n", totalMem);
+
+    /* adding in size of over all managing structs used */
+    totalMemAll = totalMem + sizeof(WOLFSSL_HEAP) + sizeof(WOLFSSL_HEAP_HINT);
+
+    /* account for max size needed for alignment of pointer */
+    totalMemAll += WOLFSSL_STATIC_ALIGN - 1;
+
+    printf("Calculated total memory for buckets, heap hint struct and "
+            "alignment is %d\n", totalMemAll);
+
+    buf = (byte*)malloc(totalMemAll);
+    printf("Return of static buffer sz is %d\n",
+        wolfSSL_StaticBufferSz_ex(4, buck, dist, buf, totalMem, 0));
+    printf("\n");
+
+    /* divide up the buffer into individual buckets and manager */
+    if (wc_LoadStaticMemory_ex(&heapHint, 4, buck, dist, buf, totalMemAll, 0,
+            0) != 0) {
+        printf("Failed to load up static memory\n");
+    }
+
+    /* test checking out all buckets */
+    for (i = 0; i < sizeof(testPtr)/sizeof(byte*); i++) {
+        printf("Checking out bucket %d size of %d...", i, buck[k]);
+        testPtr[i] = (byte*)XMALLOC(buck[k], heapHint, DYNAMIC_TYPE_TMP_BUFFER);
+        if (testPtr[i] == NULL) {
+            printf("fail\n");
+        }
+        else {
+            printf("ok\n");
+        }
+
+        k++;
+        if (i == 2) k--;
+    }
+
+    /* free all buckets back to heap hint manager */
+    for (i = 0; i < sizeof(testPtr)/sizeof(byte*); i++) {
+        XFREE(testPtr[i], heapHint, DYNAMIC_TYPE_TMP_BUFFER);
+    }
+
+    free(buf);
+    wolfCrypt_Cleanup();
+    return 0;
+}