Add 'PracticingC/' from commit 'ef128a996fc826339bbc3d9deea376932caf6981'

git-subtree-dir: PracticingC
git-subtree-mainline: fd87ec8fe9
git-subtree-split: ef128a996f

PracticingC/.gitignore

@@ -0,0 +1,6 @@
+*
+!gowrikumar/bin
+!gdbtut/bin
+!*.i
+!*.s
+!*.c

PracticingC/Makefile

@@ -0,0 +1,21 @@
+CD = cd
+RM = rm -v
+
+CC := gcc
+CFLAGS := -std=c99 -Wall -g
+
+ALL_TARGETS := $(patsubst %.c,%,$(wildcard *.c))
+
+export CD RM CFLAGS
+
+
+all: $(ALL_TARGETS)
+	$(CD) gowrikumar && $(MAKE)
+	$(CD) gdbtut && $(MAKE)
+
+clean:
+	$(CD) gowrikumar && $(MAKE) clean
+	$(CD) gdbtut && $(MAKE) clean
+
+
+.PHONY: all clean

PracticingC/README

@@ -0,0 +1,3 @@
+I don't get paid to write C for a living, so I have to sneak in practice here
+and there.  Maybe once the kiddo goes to college I can become a kernel hacker
+:-P (assuming there's still such a thing as a kernel.)

PracticingC/gdbtut/Makefile

@@ -0,0 +1,14 @@
+# tutorial exercises from http://www.unknownroad.com/rtfm/gdbtut/
+
+BINDIR := $(PWD)/bin
+export BINDIR
+
+
+all:
+	$(CD) src && $(MAKE)
+
+clean:
+	$(RM) $(BINDIR)/*
+
+
+.PHONY: all clean

PracticingC/gdbtut/src/Makefile

@@ -0,0 +1,12 @@
+# tutorial exercises from http://www.unknownroad.com/rtfm/gdbtut/
+
+ALL_BIN := $(patsubst %.c,$(BINDIR)/%,$(wildcard *.c))
+
+
+$(BINDIR)/%: %.c
+	$(CC) $(CFLAGS) -o $@ $<
+
+all: $(ALL_BIN)
+
+
+.PHONY: all

PracticingC/gdbtut/src/segfault.c

@@ -0,0 +1,28 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char **argv)
+{
+    char *buf;
+    long long huge = 8000000000000000000;
+    /* Okay, so this is *not* going to segfault because
+     * the way memory is allocated has changed since
+     * the tutorial was written.  The segfault is supposed
+     * to happen when more memory is allocated than is
+     * available on the machine.  So much for that exercise.
+     */
+
+    buf = malloc(huge);
+
+    fgets(buf, 1024, stdin);
+    printf("%s\n", buf);
+
+    return 1;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/Makefile

@@ -0,0 +1,14 @@
+# puzzles from http://www.gowrikumar.com/c/
+
+BINDIR := $(PWD)/bin
+export BINDIR
+
+
+all:
+	$(CD) src && $(MAKE)
+
+clean:
+	$(RM) $(BINDIR)/*
+
+
+.PHONY: all clean

PracticingC/gowrikumar/src/00-sizeof.c

@@ -0,0 +1,23 @@
+#include <stdio.h>
+
+
+int array[] = {23, 34, 12, 17, 204, 99, 16};
+#define TOTAL_ELEMENTS sizeof(array) / sizeof(array[0])
+
+
+int main()
+{
+    int d;
+
+#ifdef DEBUG
+    printf("sizeof(array) = %d\n", TOTAL_ELEMENTS);
+#endif
+
+    for (d = 0; d < TOTAL_ELEMENTS ; d++)
+        printf("%d\n", array[d]);
+
+    return 0;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/02-dowhile.c

@@ -0,0 +1,20 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+int main()
+{
+    int i = 1;
+    do
+    {
+        printf("%d\n", i);
+    } while(++i < 15);
+    return 0;
+}
+
+
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/03-stdoutbuf.c

@@ -0,0 +1,22 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+
+int main()
+{
+    printf("(Hit ^C to stop the madness.)\n");
+    while(1)
+    {
+        fprintf(stdout, "hello-out ");
+        fprintf(stderr, "hello-err ");
+        sleep(1);
+    }
+    return 0;
+}
+
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/03b-stdoutbuf.c

@@ -0,0 +1,23 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+
+int main()
+{
+    printf("This time we'll include \\n!\n");
+    printf("(Hit ^C to stop the madness.)\n");
+    while(1)
+    {
+        fprintf(stdout, "hello-out\n");
+        fprintf(stderr, "hello-err\n");
+        sleep(1);
+    }
+    return 0;
+}
+
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/03c-stdoutbuf.c

@@ -0,0 +1,24 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+
+int main()
+{
+    printf("This time we'll flush stdout!\n");
+    printf("(Hit ^C to stop the madness.)\n");
+    while(1)
+    {
+        fprintf(stdout, "hello-out ");
+        fprintf(stderr, "hello-err ");
+        fflush(stdout);
+        sleep(1);
+    }
+    return 0;
+}
+
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/04-macrodef.c

@@ -0,0 +1,19 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+#define f(a, b) a##b
+#define g(a) #a
+#define h(a) g(a)
+
+int main()
+{
+    printf("%s\n", h(f(1, 2)));
+    printf("%s\n", g(f(1, 2)));
+    return 0;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/04b-macrodef.c

@@ -0,0 +1,42 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+#define f(a, b) a##b
+#define g(a) #a
+#define h(a) g(a)
+#define border(c) \
+    for (int i = 0; i < 60; i++) { \
+        printf(c); \
+    } \
+    printf("\n");
+
+int main()
+{
+    printf("%s\n", h(f(1, 2)));
+    printf("%s\n", g(f(1, 2)));
+
+    printf("%s\n", g(printf("dogs rule cats drool\n")));
+
+    char * hambones = "Cats! " g(ham);
+    char * bonesham = "Meats! " g(bones);
+    char * tmp;
+
+    border("-");
+    printf("bonesham = %s\n", bonesham);
+    printf("hambones = %s\n", hambones);
+
+    border("-");
+    tmp = f(ham, bones);
+    f(ham, bones) = f(bones, ham);
+    f(bones, ham) = tmp;
+
+    printf("bonesham = %s\n", bonesham);
+    printf("hambones = %s\n", hambones);
+    return 0;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/05-switchint.c

@@ -0,0 +1,24 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include<stdio.h>
+int main()
+{
+    int a=10;
+    switch(a)
+    {
+        case '1':
+            printf("ONE\n");
+            break;
+        case '2':
+            printf("TWO\n");
+            break;
+        defa1ut:
+            printf("NONE\n");
+    }
+    return 0;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/05b-switchint.c

@@ -0,0 +1,32 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#define MAGIC_NUMBER 10
+
+#include<stdio.h>
+int main()
+{
+    int a = MAGIC_NUMBER;
+    switch(a)
+    {
+        case '1':
+            printf("ONE\n");
+            break;
+        case '2':
+            printf("TWO\n");
+            break;
+        defalut:
+            printf("NO CAN SPELL\n");
+            break;
+        defau1t:
+            printf("SO CLOSE, YET SO FAR\n");
+            break;
+        default:
+            printf("NONE\n");
+    }
+    return 0;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/06-ia64segfault.c

@@ -0,0 +1,16 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdlib.h>
+
+int main()
+{
+    int* p;
+    p = (int*)malloc(sizeof(int));
+    *p = 10;
+    return 0;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/06b-ia64segfault.c

@@ -0,0 +1,29 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+
+int main()
+{
+    int* p;
+
+    size_t size_of_int = sizeof(int);
+    printf("sizeof(int) = %d\n", size_of_int);
+
+    p = (int*)malloc(sizeof(int));
+
+    size_t size_of_p = sizeof(p);
+    printf("sizeof(p) = %d\n", size_of_p);
+
+    *p = 10;
+
+    size_t size_of_ptr_p = sizeof(*p);
+    printf("sizeof(*p) = %d\n", size_of_ptr_p);
+
+    return 0;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/07-countbits.c

@@ -0,0 +1,40 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+static unsigned int mask[] = {
+    0x55555555,
+    0x33333333,
+    0x0F0F0F0F,
+    0x00FF00FF,
+    0x0000FFFF
+};
+
+
+int get_bit_count(unsigned int x)
+{
+
+    int i;
+    int shift; /* Number of positions to shift to right*/
+    for (i = 0, shift = 1; i < 5; i++, shift *= 2) {
+        x = (x & mask[i]) + ((x >> shift) & mask[i]);
+    }
+    return x;
+}
+
+
+int main()
+{
+    int to_test[] = {0, 5, 7};
+    int current;
+
+    for (int i = 0; i < 3 ; i++) {
+        current = to_test[i];
+        printf("get_bit_count(%d) = %d\n", current, get_bit_count(current));
+    }
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/07b-countbits.c

@@ -0,0 +1,67 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+static unsigned int mask[] = {
+    0x55555555,
+    0x33333333,
+    0x0F0F0F0F,
+    0x00FF00FF,
+    0x0000FFFF
+};
+
+
+int get_bit_count(unsigned int x)
+{
+    printf("get_bit_count(%d)\n", x);
+
+    int i;
+    int x_and_mask;
+    int x_shifted;
+    int x_shifted_and_mask;
+    int shift; /* Number of positions to shift to right*/
+    for (i = 0, shift = 1; i < 5; i++, shift *= 2) {
+        printf("    START loop\n");
+        printf("        i = %d, x = %d, shift = %d\n", i, x, shift);
+
+        x_and_mask = x & mask[i];
+        printf("        x & mask[i] = %d\n", x_and_mask);
+
+        x_shifted = x >> shift;
+        printf("        x >> shift = %d\n", x_shifted);
+
+        x_shifted_and_mask = x_shifted & mask[i];
+        printf("        (x >> shift) & mask[i] = %d\n", x_shifted_and_mask);
+
+        x = x_and_mask + x_shifted_and_mask;
+        printf("        x = %d\n", x);
+        printf("    END loop\n");
+    }
+
+    return x;
+}
+
+
+int main()
+{
+    int to_test[] = {0, 5, 7};
+    int current;
+
+    /*
+    size_t mask_len = sizeof(mask) / sizeof(unsigned int);
+
+    for (int i = 0; i < mask_len; i++) {
+        printf("mask[%d] = %d\n", i, mask[i]);
+    }
+    */
+
+    for (int i = 0; i < 3 ; i++) {
+        current = to_test[i];
+        printf("get_bit_count(%d) -> %d\n", current, get_bit_count(current));
+    }
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/08-incrfloat.c

@@ -0,0 +1,26 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+int main()
+{
+    float f = 0.0f;
+    int i;
+
+    for (i = 0; i < 10; i++) {
+        f = f + 0.1f;
+    }
+
+    if (f == 1.0f) {
+        printf("f is 1.0 \n");
+    } else {
+        printf("f is NOT 1.0\n");
+    }
+
+    return 0;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/08b-incrfloat.c

@@ -0,0 +1,43 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+#include <math.h>
+
+int main()
+{
+    float f = 0.0f;
+    int i;
+
+    for (i = 0; i < 10; i++) {
+        f = f + 0.1f;
+    }
+
+    if (f == 1.0) {
+        printf("f is 1.0 \n");
+        /* nope! */
+    }
+
+    if (f == 1.000000) {
+        printf("f is perhaps 1.000000?\n");
+        /* nope again */
+    }
+
+    printf("f is neither 1.0 nor 1.000000\n");
+    printf("(f is really %.24f)\n", f);
+    printf("OH NOES!\n");
+    printf("But...\n");
+
+    double difference = fabs(f - 1.000000);
+
+    if (difference < 0.00001) {
+        printf("f is close enough to 1.000000 (off by %.24f)\n", difference);
+        /* yes? */
+    } 
+
+    return 0;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/09-multipleassignment.c

@@ -0,0 +1,20 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+int main()
+{
+    /* FIXME: the comma after "a = 1" makes the compiler angry.  Either the
+     * ", 2" should be removed or another assignment should be added.
+    int a = 1, 2;
+    */
+    int a = 1, b = 2;
+    printf("a: %d\n", a);
+    printf("b: %d\n", b);
+    return 0;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/10-nestedprintf.c

@@ -0,0 +1,15 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+int main()
+{
+    int i = 43;
+    printf("%d\n", printf("%d", printf("%d", i)));
+    return 0;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/10b-nestedprintf.c

@@ -0,0 +1,17 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+int main()
+{
+    int i = 43, nprinted;
+    nprinted = printf("%d\n", printf("%d", printf("%d", i)));
+    nprinted = printf("(the last one was %d characters)\n", nprinted);
+    nprinted = printf("(and that was %d characters)\n", nprinted);
+    return 0;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/11-duff.c

@@ -0,0 +1,37 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+void duff(register char *to, register char *from, register int count)
+{
+    register int n = (count + 7) / 8;
+    switch (count % 8) {
+        case 0: do { *to++ = *from++;
+        case 7: *to++ = *from++;
+        case 6: *to++ = *from++;
+        case 5: *to++ = *from++;
+        case 4: *to++ = *from++;
+        case 3: *to++ = *from++;
+        case 2: *to++ = *from++;
+        case 1: *to++ = *from++;
+        } while (--n > 0);
+    }
+}
+
+int main()
+{
+    char * to = "dogs cats babies";
+    char * from = "monkey hat pants";
+    int i = 16;
+    printf("to = %s\n", to);
+    printf("from = %s\n", from);
+    /* And here comes the segfault... */
+    duff(to, from, i);
+    printf("to = %s\n", to);
+    printf("from = %s\n", from);
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/11b-duff.c

@@ -0,0 +1,40 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+void duff(register char *to, register char *from, register int count)
+{
+    register int n;
+
+    int remainder = count % 8;
+    if (remainder == 0) {
+        n = (count + 7) / 8;
+        do {
+            *to++ = *from++;
+        } while (--n > 0);
+    } else if (remainder <= 7 && remainder > 0) {
+        int i;
+        int c;
+        for (i = 0; (c = from[i] && c != EOF); i++) {
+            to[i] = c;
+        }
+    }
+}
+
+int main()
+{
+    char * to = "dogs cats babies";
+    char * from = "monkey hat pants";
+    int i = 11;
+    printf("to = %s\n", to);
+    printf("from = %s\n", from);
+    /* And here comes the segfault... */
+    duff(to, from, i);
+    printf("to = %s\n", to);
+    printf("from = %s\n", from);
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/12-countbits2.c

@@ -0,0 +1,32 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+
+int get_bit_count(unsigned int x)
+{
+    int count=0;
+    while(x)
+    {
+        count++;
+        x = x&(x-1);
+    }
+    return count;
+}
+
+
+int main()
+{
+    int to_test[] = {0, 5, 7};
+    int current;
+
+    for (int i = 0; i < 3 ; i++) {
+        current = to_test[i];
+        printf("get_bit_count(%d) = %d\n", current, get_bit_count(current));
+    }
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

PracticingC/gowrikumar/src/Makefile

@@ -0,0 +1,12 @@
+# puzzles from http://www.gowrikumar.com/c/
+
+ALL_BIN := $(patsubst %.c,$(BINDIR)/%,$(wildcard *.c))
+
+
+$(BINDIR)/%: %.c
+	$(CC) $(CFLAGS) -o $@ $<
+
+all: $(ALL_BIN)
+
+
+.PHONY: all

PracticingC/socky.c

@@ -0,0 +1,48 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sys/un.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+
+const char *SOCKNAME = "/tmp/socky";
+int sfd;
+struct sockaddr_un addr;
+
+
+int main(int argc, char *argv[])
+{
+    sfd = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (sfd == -1) {
+        fprintf(stderr, "FAILED TO ALLOCATE SOCKET\n");
+        goto error;
+    }
+
+    memset(&addr, 0, sizeof(struct sockaddr_un));
+    addr.sun_family = AF_UNIX;
+    strncpy(addr.sun_path, SOCKNAME, sizeof(addr.sun_path) - 1);
+
+    if (bind(sfd, (struct sockaddr *)&addr, sizeof(struct sockaddr_un)) == -1) {
+        fprintf(stderr, "FAILED TO BIND SOCKET TO ADDRESS\n");
+        goto error;
+    }
+
+    if (listen(sfd, 128) == -1) {
+        fprintf(stderr, "FAILED TO LISTEN ON ADDRESS\n");
+        goto error;
+    }
+
+    for (;;) {
+        fprintf(stdout, "ATTEMPTING TO WAIT FOR REQUEST ON %s\n", SOCKNAME);
+        if (accept(sfd, NULL, NULL) == -1) {
+            fprintf(stderr, "FAILED TO ACCEPT REQUEST ON ADDRESS\n");
+            goto error;
+        }
+    }
+
+    return 0;
+
+error:
+    return 1;
+
+}