add few more

5 files changed, 266 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 67ad147..2e1d8c1 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 BINS = ascii class depipe_strings dup fpipe pipe realloc strpbrk strsep \
        tokenizer getopt prime_mask linked_list pi_bbp string_tokenizer  \
-       tcpserver tcpclient regexp
+       tcpserver tcpclient regexp c99 asm playground_05-25-2011
 
 CURL = curl_tomem curl_tofile
 
diff --git a/asm.c b/asm.c
new file mode 100644
index 0000000..301a767
--- /dev/null
+++ b/asm.c
@@ -0,0 +1,13 @@
+#include <stdio.h>
+
+int main(int argc, char *argv[])
+{
+    int i = 12;
+
+    asm(".att_syntax prefix");
+    asm("movl %0, %%eax\n" : : "r" (i) : "eax");
+    printf("i is: %d\n", i);
+
+    return 0;
+}
+
diff --git a/asm2.c b/asm2.c
new file mode 100644
index 0000000..7621b78
--- /dev/null
+++ b/asm2.c
@@ -0,0 +1,65 @@
+/*
+ * So far I cannot figure out how I used to compile this :/
+ * asm(".intel_syntax prefix");
+ *
+ */
+
+#include <stdio.h>
+
+void asm_summation(int *n)
+{
+    asm("xor eax, eax  \n" /* summation */
+        "mov ecx, 0    \n" /* counter */
+        "mov edx, %0   \n" /* end */
+        "_loop:        \n"
+        "add eax, ecx  \n"
+        "inc ecx       \n"
+        "cmp ecx, edx  \n"
+        "jle _loop     \n"
+        "mov %0, eax   \n" : "=r" (*n) : "r" (*n) : "eax");
+}
+
+void asm_summation2(int *n)
+{
+    if (*n <= 1)
+    {
+        *n = 0;
+        return;
+    }
+
+    asm("xor eax, eax  \n" /* summation */
+        "mov ecx, %0   \n" /* counter */
+        "_loop2:       \n"
+        "add eax, ecx  \n"
+        "loop _loop2   \n"
+        "mov %0, eax   \n" : "=r" (*n) : "r" (*n) : "eax");
+}
+
+void asm_rotate(int *n)
+{
+    asm("mov eax, %0   \n"
+        "rol eax, 1    \n"
+        "mov %0, eax   \n" : "=r" (*n) : "r" (*n) : "eax");
+}
+
+int main(int argc, char *argv[])
+{
+    int i = 12;
+
+
+
+    /* output, input (r) = register, clobbered */
+    asm("mov eax, %0\n" : : "r" (i) : "eax");
+    printf("i is: %d\n", i);
+
+    int j = -1;
+    asm_summation2(&j);
+    printf("summation is %d\n", j);
+
+    int k = 2;
+    asm_rotate(&k);
+    printf("k = %d\n", k);
+
+    return 0;
+}
+
diff --git a/c99.c b/c99.c
new file mode 100644
index 0000000..d9b4357
--- /dev/null
+++ b/c99.c
@@ -0,0 +1,46 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <memory.h>
+
+struct node
+{
+    int x;
+    int y;
+    int z;
+
+    char name[21];
+};
+typedef struct node node_t;
+
+void mymemset(void *mem, char c, unsigned int n)
+{
+    char *p = (char *) mem;
+
+    while (n--)
+        *p++ = c;
+}
+
+void func(int arr[])
+{
+    printf("the size of arr is: %lu\n", sizeof(arr));
+    arr[0] = 9;
+}
+
+int main(int argc, char *argv[])
+{
+    node_t *p = (node_t *) malloc(sizeof(node_t) + 21); /* c99 */
+    strcpy(p->name, "I have a long name");
+
+    printf("%s", p->name);
+
+    int myarr[] = { 1,2,3,4,5,6,7,8,9,10 };
+    func(myarr);
+
+    printf("%d\n", myarr[0]);
+
+    mymemset(p, -1, sizeof(node_t));
+
+    return 0;
+}
+
diff --git a/playground_05-25-2011.c b/playground_05-25-2011.c
new file mode 100644
index 0000000..20249a7
--- /dev/null
+++ b/playground_05-25-2011.c
@@ -0,0 +1,141 @@
+/*
+ * playground_05-25-2011.c
+ *
+ *
+ * Playing around with unions and macros, and how both
+ * of these things look in the memory
+ *
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+
+#define EXP(base, exp, ret) do {     \
+        int i;                       \
+        int acc = 1;                 \
+        for (i = 0; i < exp; i++)    \
+            acc *= base;             \
+        ret = acc;                   \
+    } while(0)                       \
+
+#define MUL(base, mult, ret) do {    \
+        int i;                       \
+        int acc = 0;                 \
+        for (i = 0; i < mult; i++)   \
+            acc += base;             \
+        ret = acc;                   \
+    } while(0)                       \
+
+/* trace a variable, requires ANSI compliant compiler */
+#define TRACE(var, fmt) \
+    printf("TRACE: " #var " = " #fmt ", %s:%d\n", var, __FILE__, __LINE__)
+
+#pragma pack(1)
+struct UART_tag
+{
+    union
+    {
+        struct
+        {
+            uint32_t baud_rate; /* bits [0:31] */
+
+            uint8_t tx_en : 1;
+            uint8_t rx_en : 1;
+            uint8_t parity : 1; /* bit [34], 35th */
+
+            uint32_t : 29;
+
+        } B;
+
+        uint64_t R;
+    } SET;
+
+};
+typedef struct UART_tag UART_t;
+
+void UART_info(UART_t *dev)
+{
+    printf("baud rate: %u\n"
+           "tx enabled: %s\n"
+           "rx enabled: %s\n"
+           "parity enabled: %s\n", dev->SET.B.baud_rate,
+                               dev->SET.B.tx_en ? "yes" : "no",
+                               dev->SET.B.rx_en ? "yes" : "no",
+                               dev->SET.B.parity ? "yes" : "no");
+}
+
+void dumpHex(UART_t *p, unsigned int sz)
+{
+    int i;
+    for (i = 0; i < sz; i++)
+    {
+        if (i % 4 == 0)
+            printf("%s0x%08x: ", i == 0 ? "" : "\n", i);
+
+        printf(" 0x%02x", ((unsigned char *) p)[i] );
+    }
+    printf("\n\n");
+}
+
+int main(int argc, char **argv)
+{
+    /* assigning a struct within the union */
+    puts("\t assigning a struct within the union");
+    UART_t myUart;
+	myUart.SET.R = 0;
+    myUart.SET.B.baud_rate = 19200;
+    myUart.SET.B.tx_en = 1;
+    myUart.SET.B.rx_en = 1;
+    myUart.SET.B.parity = 0;
+
+    UART_info(&myUart);
+    puts("");
+
+    puts("\t this is how UART_t looks in the memory");
+    dumpHex(&myUart, sizeof(UART_t));
+
+    /* disable a flag within the struct */
+    puts("\t disable a flag within the struct");
+    myUart.SET.B.tx_en = 0;
+    UART_info(&myUart);
+    puts("");
+
+    /* modifying the whole structure at once */
+    puts("\t modifying the whole structure at once");
+    myUart.SET.R = 0;
+    UART_info(&myUart);
+    puts("");
+
+    /* enable the parity bit */
+    myUart.SET.R |= (uint64_t) \
+                    ((uint64_t) 1 << (64 - 30)); /* this is inverted compared
+                                                  * to how it would be done on
+                                                  * a register */
+
+    puts("\t setting the parity bit to ON using logical OR operator");
+    UART_info(&myUart);
+    puts("");
+
+    printf("size of UART_t is: %lu bytes\n", sizeof(UART_t));
+    printf("size of UART_tag is: %lu bytes\n", sizeof(myUart.SET.B));
+
+    int x;
+    EXP(2, 20, x);
+    printf("a megabyte is %d bytes\n", x);
+
+    int y;
+    MUL(x, 4, y);
+    printf("4 megabytes is %d bytes\n", y);
+
+    /* endianess */
+    int z = 1;
+    if (*((unsigned char *) &z) == 1)
+        puts("machine has a little-endian byte ordering");
+    else
+        puts("machine has a big-endian byte ordering");
+
+    TRACE(y, %d);
+
+    return 0;
+}
+