Master the technology of Dachang in one class Commission and reflection

Confusing "high-end" mechanics

Confusing delegation mechanism:

UseC language, understand the delegation mechanism from the bottom layer

// Commission 1: Computer Science and Technology Education void computerEdu(const char* name) { printf("%s study: operating system\n", name); printf("%s study: computer compositionPrinciple\n", name); printf("%s study: data structure\n", name); printf("%s study: data logic circuit\n", name); printf("%s study: compilation principle\n", name); }// Delegate 2: Physical Education void tiYuEdu(const char* name) { printf("%s study: basketball\n"); printf("%s study: athletics\n");printf("%s study: Baduanjin\n"); printf("%s study: football\n");}void xiangQing(const char* name) { printf("%s, 10,000 characters are omitted here....\n", name); }// university("Zhang San", computerEdu); // Execute:stuNmae = "Zhang San" edu = computerEdu void university(const char* stuNmae, void(*edu)(const char*)) { edu(stuNmae); }int main(void) { university("Zhang San", computerEdu); university("Zhang San", tiYuEdu); university("Zhang San", xiangQing); }

Confusing reflection mechanism: (Javareflection mechanism)

UseC language, understand the reflection mechanism from the bottom layer

struct node { const char* name; void (*func)(); };struct node nodes[] = { {"fishing", diaoYu}, {"code", luMa}, {"eat", eat},{"Swimming", youyong}, };// Parameters: favorite activity name void findLove(const char* name) { int count = sizeof(nodes) / sizeof(nodes[0]); for (int i = 0;i < count; i++) { if (strcmp(name, nodes[i].name) == 0) { nodes[i].func(); return; } } }

Optimization:Use the compiler's precompiled instructions to define the data segment (compiled only by gcc/g++support)

#include  #include  #include  typedef void(*calc_t)(int, int); typedef struct { const char* name; calc_t fn;} node_t; // only supported by gcc!#define SEC __attribute__((__section__("ss"), aligned(sizeof(node_t)))) void f1(int a, int b) { printf("%s %d %d %d\n", __func__, __LINE__, a, b); }void f2(int a, int b) { printf("%s %d %d %d\n", __func__, __LINE__, a, b); }// The compiler will automatically provide __start_ss, __stop_ss mark the start and end addresses of segment ss extern size_t __start_ss; extern size_t __stop_ss;// The structure variable a is located in the custom section ss node_t a SEC = { "cmd1", f1 }; void do_callback(const char* name) { size_t i; for (node_t* p = &__start_ss; p < &__stop_ss; p++) {if (!strcmp(p->name, name)) { return p->fn(1, 2); } } }// The structure variable b is located in the custom segment ss node_t b SEC = { "cmd2", f2 }; int main(int argc, char** argv) { do_callback("cmd2"); return 0; }

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