Chapter 5

7 files changed, 274 insertions, 2 deletions

diff --git a/ex1-8.c b/ex1-8.c
index 7e8c3bd..3ba90d0 100644
--- a/ex1-8.c
+++ b/ex1-8.c
@@ -32,7 +32,7 @@ static struct res _loop(struct res res) {
   } else if (c == '\t') {
     res.tb++;
   }
-  __attribute__((musttail))
+  //__attribute__((musttail))
   return _loop(res);
 }
 
diff --git a/ex5-1.c b/ex5-1.c
new file mode 100644
index 0000000..9a43c00
--- /dev/null
+++ b/ex5-1.c
@@ -0,0 +1,97 @@
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define PUSHBACK_MAX 10
+typedef struct {
+    FILE* stream;
+    int pushback[PUSHBACK_MAX];
+    int pushback_ix;
+} StreamWithPushback;
+
+StreamWithPushback swpb_new(FILE* f) {
+    StreamWithPushback ret;
+    ret.stream = f;
+    ret.pushback_ix = 0;
+    for (int i=0; i<PUSHBACK_MAX; i++) {
+        ret.pushback[i] = -1;
+    }
+    return ret;
+}
+
+int getch(StreamWithPushback* swpb) {
+    if (swpb->pushback_ix > 0) {
+        int ch = swpb->pushback[swpb->pushback_ix];
+        swpb->pushback_ix--;
+        return ch;
+    }
+    return getc(swpb->stream);
+}
+
+void ungetch(StreamWithPushback* swpb, int ch) {
+    if (swpb->pushback_ix >= PUSHBACK_MAX) {
+        fprintf(stderr, "pushback buffer was full!\n");
+        exit(1);
+    }
+    swpb->pushback[swpb->pushback_ix] = ch;
+    swpb->pushback_ix++;
+}
+
+/* getint:  get next integer from input into *pn */
+int getint(StreamWithPushback* swpb, int *pn) {
+    int c, sign;
+
+    while (isspace(c = getch(swpb))) {}
+
+    if (!isdigit(c) && c != EOF && c != '+' && c != '-') {
+        ungetch(swpb, c);
+        return 0;
+    }
+
+    sign = (c == '-') ? -1 : 1;
+    if (c == '+' || c == '-') {
+        c = getch(swpb);
+        // If c isn't then a digit, then we don't have a number.
+        if (!isdigit(c)) {
+            ungetch(swpb, c);
+            // Push the sign character back as well, don't consume it
+            ungetch(swpb, sign == -1 ? '-' : '+');
+            return 0;
+        }
+    }
+
+    for (*pn = 0; isdigit(c); c = getch(swpb)) {
+        *pn = 10 * *pn + (c - '0');
+    }
+    *pn *= sign;
+
+    if (c != EOF) {
+        ungetch(swpb, c);
+    }
+    return c;
+}
+
+#ifndef test
+
+int main(void) {
+    int p, x;
+    StreamWithPushback swpb = swpb_new(stdin);
+    while ((x = getint(&swpb, &p)) != EOF) {
+        if (x > 0) {
+            printf("%d\n", p);
+        } else {
+            printf("not a number!\n");
+        }
+    } 
+}
+
+#else
+
+#include "CuTest.h"
+
+// I could write unit tests here, using fmemopen
+// instead of reading something off the filesystem.
+
+// But I can't be bothered.
+
+#endif
\ No newline at end of file
diff --git a/ex5-3.c b/ex5-3.c
new file mode 100644
index 0000000..826a581
--- /dev/null
+++ b/ex5-3.c
@@ -0,0 +1,20 @@
+#include <stdio.h>
+
+void z_strcat(char* s, char* t) {
+    // Skip to the end of s
+    for (; *s != '\0'; s++) {}
+    // Copy over t
+    for (; *t != '\0'; t++, s++) {
+        *s = *t; 
+    }
+    // Ensure null terminator
+    *s = '\0';
+}
+
+int main(void) {
+    char buf[100] = "";
+    z_strcat(buf, "foo");
+    printf("%s\n", buf);
+    z_strcat(buf, "bar");
+    printf("%s\n", buf);
+}
\ No newline at end of file
diff --git a/ex5-4.c b/ex5-4.c
new file mode 100644
index 0000000..d32e965
--- /dev/null
+++ b/ex5-4.c
@@ -0,0 +1,23 @@
+#include <stdio.h>
+
+int strend(char* const s, char* const t) {
+    char* s_p = s;
+    char* t_p = t;
+    for (; *s_p != '\0'; s_p++);
+    for (; *t_p != '\0'; t_p++);
+    for (; !(s_p == s || t_p == t); s_p--, t_p--) {
+        if (*s_p != *t_p) {
+            return 0;
+        }
+    }
+    return t_p == t;
+}
+
+int main(void) {
+    printf("0==%d\n", strend("foo", "bar"));
+    printf("1==%d\n", strend("foo", "foo"));
+    printf("1==%d\n", strend("xyzfoo", "foo"));
+    printf("0==%d\n", strend("foo", "xyzfoo"));
+    printf("1==%d\n", strend("foo", ""));
+    printf("1==%d\n", strend("", ""));
+}
\ No newline at end of file
diff --git a/ex5-5.c b/ex5-5.c
new file mode 100644
index 0000000..a6af275
--- /dev/null
+++ b/ex5-5.c
@@ -0,0 +1,20 @@
+#include <stdio.h>
+
+char* z_strncpy(char *dest, char *src, size_t n) {
+    char* max = dest + n;
+    for (; *src != '\0' && dest < max; dest++, src++) {
+        *dest = *src;
+    }
+    for (; dest < max; dest++) {
+        *dest = '\0';
+    }
+    return dest;
+}
+
+int main(void) {
+    char buf[100] = "";
+    z_strncpy(buf, "Hello, World", 5);
+    printf("Hello = %s\n", buf);
+    z_strncpy(buf, "Hello, World", 20);
+    printf("Hello, World = [%s]\n", buf);
+}
\ No newline at end of file
diff --git a/ex5-7.c b/ex5-7.c
new file mode 100644
index 0000000..2d277ad
--- /dev/null
+++ b/ex5-7.c
@@ -0,0 +1,111 @@
+#include <stdio.h>
+#include <string.h>
+
+// An extremely simple allocation system.
+// Memory must be freed in the reverse order it was allocated.
+#define ALLOCSIZE 10000
+
+static char allocbuf[ALLOCSIZE];
+static char *allocp = allocbuf;
+
+char *alloc(int n) {
+    if (allocbuf + ALLOCSIZE - allocp >= n) {
+        allocp += n;
+        return allocp - n;
+    } else {
+        return NULL;
+    }
+}
+
+void afree(char *p) {
+    if (p >= allocbuf && p < allocbuf + ALLOCSIZE) {
+        allocp = p;
+    }
+}
+
+#define MAXLINES 5000
+
+int readlines(char* lineptr[], int nlines);
+
+void writelines(char* lineptr[], int nlines);
+
+void qsort(char* lineptr[], int left, int right);
+
+int main() {
+    int nlines;
+    char* lineptr[MAXLINES];
+    if ((nlines = readlines(lineptr, MAXLINES)) >= 0) {
+        qsort(lineptr, 0, nlines-1);
+        writelines(lineptr, nlines);
+        return 0;
+    } else {
+        fprintf(stderr, "error: input too big to sort\n");
+        return 1;
+    }
+}
+
+#define MAXLEN 1000
+
+int z_getline(char*, int);
+char* alloc(int);
+
+int readlines(char* lineptr[], int maxlines) {
+    int len; 
+    int nlines = 0;
+    char* p;
+    char line[MAXLEN];
+    while ((len = z_getline(line, MAXLEN)) > 0) {
+        if (nlines >= maxlines || (p = alloc(len)) == NULL) {
+            return -1;
+        } else {
+            line[len-1] = '\0'; // delete newline
+            strcpy(p, line);
+            lineptr[nlines++] = p;
+        }
+    }
+    return nlines;
+}
+
+void writelines(char* lineptr[], int nlines) {
+    for (int i=0; i<nlines; i++)
+        printf("%s\n", lineptr[i]);
+}
+
+void qsort(char* v[], int left, int right) {
+    int i, last;
+    void swap(char* v[], int i, int j);
+    if (left >= right) {
+        return;
+    }
+    swap(v, left, (left+right)/2);
+    last = left;
+    for (i=left+1; i<=right; i++) {
+        if (strcmp(v[i], v[left]) < 0) {
+            swap(v, ++last, i);
+        }
+    }
+    swap(v, left, last);
+    qsort(v, left, last-1);
+    qsort(v, last+1, right);
+}
+
+void swap(char* v[], int i, int j) {
+    char* temp = v[i];
+    v[i] = v[j];
+    v[j] = temp;
+}
+
+
+/* getline:  read a line into s, return length */
+int z_getline(char s[], int lim) {
+    int c, i;
+    for (i=0; i<lim-1 && (c=getchar())!=EOF && c!='\n'; ++i) {
+        s[i] = c;
+    }
+    if (c == '\n') {
+        s[i] = c;
+        ++i;
+    }
+    s[i] = '\0';
+    return i;
+}
\ No newline at end of file
diff --git a/run b/run
index 96e9fac..2efa8b5 100755
--- a/run
+++ b/run
@@ -1,6 +1,7 @@
 #!/usr/bin/env bash
 set -e
-clang -Wall -Werror -o exe $@
+CC=gcc
+${CC} -Wall -Werror -o exe $@
 ./exe
 result=$?
 rm exe