+11-struct

11-struct/CMakeLists.txt

@@ -0,0 +1,4 @@
+add_executable(musician musician.c)
+add_executable(padding offset.c)
+add_executable(sds sds.c)
+add_executable(sds-202412 sds-202412.c)

11-struct/README.md

@@ -0,0 +1,33 @@
+# `12-struct`
+
+- `struct`
+- `struct musician`
+- `typedef struct musician`
+- **struct alignment and padding**
+- `typedef struct score`
+- `enum`
+- `struct` assignment
+- `PrintMusician(const Musician m)`
+- `PrintMusician(const Musician *m)`
+
+## c-reference
+
+- `struct`
+- `flexible array`
+
+## padding
+
+## `offsetof` and `container_of`
+
+- [offsetof @ wikipedia](https://en.wikipedia.org/wiki/Offsetof)
+- [offsetof @ cref](https://en.cppreference.com/w/c/types/offsetof)
+- [offsetof @ stackoverflow](https://stackoverflow.com/q/26906621/1833118)
+- [container_of @ stackoverflow](https://stackoverflow.com/q/15832301/1833118)
+- [container_of @ radek.io](https://radek.io/posts/magical-container_of-macro/)
+- [container_of @ Linux Kernel Monkey Log](http://www.kroah.com/log/linux/container_of.html)
+- [container_of @ 0xAX](https://0xax.gitbooks.io/linux-insides/content/DataStructures/linux-datastructures-1.html)
+
+## Union
+
+- [union in
+  `dictEntry` @ redis](https://github.com/redis/redis/blob/c51c96656bf1f1801ae90a376f71890cbcdea4b4/src/dict.c#L47-L134)

11-struct/musician.c

@@ -0,0 +1,187 @@
+// Created by hfwei on 2024/12/11.
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <time.h>
+
+typedef enum gender {
+  MALE,
+  FEMALE,
+  GENDER_KINDS,
+} Gender;
+
+typedef struct score {
+  int c_score;
+  int java_score;
+  int python_score;
+} Score;
+
+typedef struct musician {
+  char *name;
+  // char gender;
+  Gender gender;
+  struct tm birth;
+
+  char *album;
+
+  Score score;
+
+  union {
+    int performances;    // number of performances
+    double funding;      // funding in millions
+    int awards;          // number of awards won
+    char *highlight;     // textual highlight of the yea
+  } year_end_summary;
+
+  enum {
+    PERFORMANCES,
+    FUNDING,
+    AWARDS,
+    HIGHLIGHT
+  } summary_type;
+} Musician;
+
+// void PrintMusician(const Musician m);
+void PrintMusician(const Musician *m);
+int CompareMusician(const void *m1, const void *m2);
+
+int main(void) {
+  printf("sizeof(Score) = %zu\n", sizeof(Score));
+  printf("sizeof(Musician) = %zu\n", sizeof(Musician));
+  printf("offsetof(Musician, name) = %zu\n", offsetof(Musician, name));
+  printf("offsetof(Musician, gender) = %zu\n", offsetof(Musician, gender));
+  printf("offsetof(Musician, album) = %zu\n", offsetof(Musician, album));
+  printf("offsetof(Musician, score) = %zu\n", offsetof(Musician, score));
+
+  Musician luo = {
+      .name = "Luo Dayou",
+      .gender = MALE,
+      .birth = {
+          .tm_year = 1954 - 1900,
+          .tm_mon = 7 - 1,
+          .tm_mday = 20,
+          .tm_wday = 2, // Tuesday
+      },
+      .album = "ZhiHuZheYe",
+      .score = {
+          .c_score = 0,
+          .java_score = 10,
+          .python_score = 20,
+      },
+      .year_end_summary.performances = 20,
+      .summary_type = PERFORMANCES,
+  };
+
+  Musician cui = {
+      .name = "Cui Jian",
+      .gender = MALE,
+      .birth = {
+          .tm_year = 1961 - 1900,
+          .tm_mon = 8 - 1,
+          .tm_mday = 2,
+          .tm_wday = 3, // Wednesday
+      },
+      .album = "XinChangZhengLuShangDeYaoGun",
+      .score = {
+          .c_score = 10,
+          .java_score = 20,
+          .python_score = 30,
+      },
+      .year_end_summary.funding = 2.5,
+      .summary_type = FUNDING,
+  };
+
+  char album[] = "YiKeBuKenMeiSuDeXin";
+  Musician zhang = {
+      .name = "Zhang Chu",
+      .gender = MALE,
+      .birth = {
+          .tm_year = 1968 - 1900,
+          .tm_mon = 11 - 1,
+          .tm_mday = 17,
+          .tm_wday = 0, // Sunday
+      },
+      // .album = "YiKeBuKenMeiSuDeXin",
+      .album = album,
+      .score = {
+          .c_score = 20,
+          .java_score = 30,
+          .python_score = 40,
+      },
+      // https://www.bilibili.com/video/BV1f6i2YZEMJ/
+      .year_end_summary.awards = 2,
+      .summary_type = AWARDS,
+  };
+
+  Musician guo = zhang;
+  guo.name = "Guo Fucheng";
+  strcpy(guo.album, "YiKeJiuMeiSuDeXin");
+  // PrintMusician(guo);
+  // PrintMusician(zhang);
+  PrintMusician(&guo);
+  PrintMusician(&zhang);
+
+  Musician musicians[] = {luo, cui, zhang,};
+  int len = sizeof musicians / sizeof *musicians;
+  for (int i = 0; i < len; ++i) {
+    // PrintMusician(musicians[i]);
+    PrintMusician(&musicians[i]);
+  }
+
+  qsort(musicians, len,
+        sizeof *musicians,
+        CompareMusician);
+
+  for (int i = 0; i < len; ++i) {
+    // PrintMusician(musicians[i]);
+    PrintMusician(&musicians[i]);
+  }
+
+  return 0;
+}
+
+// void PrintMusician(const Musician m) {
+//   printf("\n%s\t%d\t%s\t%d\t%d\t%d\n",
+//          m.name,
+//          m.gender,
+//          m.album,
+//          m.score.c_score,
+//          m.score.java_score,
+//          m.score.python_score);
+// }
+
+void PrintMusician(const Musician *m) {
+  printf("\n%s\t%d\t%s\t%s\t%d\t%d\t%d\n",
+         m->name,
+         m->gender,
+         asctime(&m->birth),
+         m->album,
+         m->score.c_score,
+         m->score.java_score,
+         m->score.python_score);
+
+  switch (m->summary_type) {
+    case PERFORMANCES:printf("Performed %d times\n", m->year_end_summary.performances);
+      break;
+    case FUNDING:printf("Secured $%.2fM in funding\n", m->year_end_summary.funding);
+      break;
+    case AWARDS:printf("Won %d awards\n", m->year_end_summary.awards);
+      break;
+    case HIGHLIGHT:printf("%s\n", m->year_end_summary.highlight);
+      break;
+  }
+}
+
+int CompareMusician(const void *m1, const void *m2) {
+  const Musician *m_left = m1;
+  const Musician *m_right = m2;
+
+  return strcmp(m_left->album, m_right->album);
+
+  // char *name_left = *(char **) m1;
+  // char *name_right = *(char **) m2;
+
+  // return strcmp(name_left, name_left);
+}

11-struct/offset.c

@@ -0,0 +1,35 @@
+// Created by hfwei on 2024/12/10.
+
+#include <stdio.h>
+//#include <stddef.h>
+
+// creference: https://en.cppreference.com/w/c/types/offsetof
+// Magic: https://radek.io/posts/magical-container_of-macro/
+// StackOverflow: https://stackoverflow.com/q/15832301/1833118
+
+#define offsetof(TYPE, MEMBER) ((size_t) &(((TYPE *)0)->MEMBER))
+//#define OffsetOf(TYPE, MEMBER) (&(((TYPE *)0)->MEMBER))
+
+#define container_of(ptr, type, member) ({                      \
+        const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
+        (type *)( (char *)__mptr - offsetof(type,member) );})
+
+typedef struct abc {
+  char a;
+  int b;
+  char c;
+} ABC;
+
+int main(void) {
+  printf("sizeof(ABC) = %zu\n", sizeof(ABC));
+  printf("offsetof(ABC, a) = %zu\n", offsetof(ABC, a));
+  printf("offsetof(ABC, b) = %zu\n", offsetof(ABC, b));
+  printf("offsetof(ABC, c) = %zu\n", offsetof(ABC, c));
+
+  ABC abc = {'a', 42, 'c'};
+  const int *b_ptr = &abc.b;
+  ABC *abc_ptr = container_of(b_ptr, ABC, b);
+  printf("address: %p\t%p\n", abc_ptr, &abc);
+
+  return 0;
+}

11-struct/sds-202412.c

@@ -0,0 +1,102 @@
+// Created by hengxin on 12/11/24.
+// sds.h: https://github.com/redis/redis/blob/unstable/src/sds.h
+// sds.c: https://github.com/redis/redis/blob/unstable/src/sds.c
+
+/* SDSLib 2.0 -- A C dynamic strings library
+ *
+ * Copyright (c) 2006-Present, Redis Ltd.
+ * All rights reserved.
+ *
+ * Licensed under your choice of the Redis Source Available License 2.0
+ * (RSALv2) or the Server Side Public License v1 (SSPLv1).
+ */
+
+#include <stdio.h>
+#include <ctype.h>
+#include <stdint.h>
+
+typedef char *sds;
+
+struct __attribute__ ((__packed__)) sdshdr5 {
+  unsigned char flags; /* 3 lsb of type, and 5 msb of string length */
+  char buf[];
+};
+
+struct __attribute__ ((__packed__)) sdshdr8 {
+  uint8_t len; /* used */
+  uint8_t alloc; /* excluding the header and null terminator */
+  unsigned char flags; /* 3 lsb of type, 5 unused bits */
+  char buf[];
+};
+
+struct __attribute__ ((__packed__)) sdshdr16 {
+  uint16_t len; /* used */
+  uint16_t alloc; /* excluding the header and null terminator */
+  unsigned char flags; /* 3 lsb of type, 5 unused bits */
+  char buf[];
+};
+
+struct unpacked_sdshdr16 {
+  uint16_t len; /* used */
+  uint16_t alloc; /* excluding the header and null terminator */
+  unsigned char flags; /* 3 lsb of type, 5 unused bits */
+  char buf[];
+};
+
+struct __attribute__ ((__packed__)) sdshdr32 {
+  uint32_t len; /* used */
+  uint32_t alloc; /* excluding the header and null terminator */
+  unsigned char flags; /* 3 lsb of type, 5 unused bits */
+  char buf[];
+};
+
+struct __attribute__ ((__packed__)) sdshdr64 {
+  uint64_t len; /* used */
+  uint64_t alloc; /* excluding the header and null terminator */
+  unsigned char flags; /* 3 lsb of type, 5 unused bits */
+  char buf[];
+};
+
+#define SDS_TYPE_5  0
+#define SDS_TYPE_8  1
+#define SDS_TYPE_16 2
+#define SDS_TYPE_32 3
+#define SDS_TYPE_64 4
+#define SDS_TYPE_MASK 7
+#define SDS_TYPE_BITS 3
+#define SDS_HDR(T, s) ((struct sdshdr##T *)((s)-(sizeof(struct sdshdr##T))))
+#define SDS_TYPE_5_LEN(f) ((f)>>SDS_TYPE_BITS)
+
+static inline int sdsHdrSize(char type) {
+  switch (type & SDS_TYPE_MASK) {
+    case SDS_TYPE_5:return sizeof(struct sdshdr5);
+    case SDS_TYPE_8:return sizeof(struct sdshdr8);
+    case SDS_TYPE_16:return sizeof(struct sdshdr16);
+    case SDS_TYPE_32:return sizeof(struct sdshdr32);
+    case SDS_TYPE_64:return sizeof(struct sdshdr64);
+  }
+  return 0;
+}
+
+static inline size_t sdslen(const sds s) {
+  unsigned char flags = s[-1];
+  switch (flags & SDS_TYPE_MASK) {
+    case SDS_TYPE_5:return SDS_TYPE_5_LEN(flags);
+    case SDS_TYPE_8:return SDS_HDR(8, s)->len;
+    case SDS_TYPE_16:return SDS_HDR(16, s)->len;
+    case SDS_TYPE_32:return SDS_HDR(32, s)->len;
+    case SDS_TYPE_64:return SDS_HDR(64, s)->len;
+  }
+  return 0;
+}
+
+int main(void) {
+  // test sdsHdrSize
+  printf("%d\n", sdsHdrSize(SDS_TYPE_5));
+  printf("%d\n", sdsHdrSize(SDS_TYPE_8));
+  printf("%d\n", sdsHdrSize(SDS_TYPE_16));
+  printf("%zu\n", sizeof(struct unpacked_sdshdr16));
+  printf("%d\n", sdsHdrSize(SDS_TYPE_32));
+  printf("%d\n", sdsHdrSize(SDS_TYPE_64));
+  return 0;
+}