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HW6

lrand48_r

lrand48_r
从一个buffer里读东西，输出31bits 随机字符到result里
因此需要srand48_r吃一段数据作为seed，先对一个buffer生成随机字符
再拿这个buffer作为lrand48_r的输入
注意目标需要64bits 随机字符，所以要位运算3次

lrand48_r(struct drand48_data *buffer, long int* result):

strict drand48_data buffer;
srand48_r(12345, &buffer);

long int rand1, rand2, rand3;
lrand48_r(&buffer, &rand1);
lrand48_r(&buffer, &rand2);
lrand48_r(&buffer, &rand3);

unsigned long long rand64 = (rand1 << 33) | (rand2 << 2) | (rand2 && 0x3);

mrand48:

mrand48
直接输出32bits 随机字符
因此位运算2次

long int rand1 = mrand48();
long int rand2 = mrand48();

long long rand64 = (rand1 << 32) | rand2;

getopt

#include "options.h"

long long process_arguments(int argc, char** argv, option* options) {
    int opt;
    while ((opt = getopt(argc, argv, "i:o:")) != -1) {
        switch (opt) {
            case 'i':
                options->input = 1;
                if (strcmp(optarg, "") == 0) {
                    fprintf(stderr, "Expected one argument for the input source.\n");
                    return -1;
                } else {
                    options->input_source = optarg;
                }
                break;
            
            case 'o':
                options->output = 1;
                if (strcmp(optarg, "") == 0) {
                    fprintf(stderr, "Expected one argument for the output source.\n");
                    return -1;
                } else {
                    options->output_source = optarg;
                }
                break;

            default:
                break;
        }
    }
    
    if (optind >= argc) {
        fprintf(stderr, "Expected one non-option argument for the number of bytes.\n");
        return -1;
    }

    errno = 0;
    char *endptr;
    long long nbytes = strtoll(argv[optind], &endptr, 10);

    if (errno != 0 || *endptr != '\0' || nbytes < 0) {
        fprintf (stderr, "%s: usage: %s NBYTES\n", argv[0], argv[0]);
        return -1;
    }

    return nbytes;
}

optind 直接指向non-optional argument after the while(opt) thus, it is refering to a nbytes in this assignment

Checklist

Here's the final study list shared today in Dis 1C (for some reason discord isn't allowing me to upload the file):

Final

When: Mon 8am Where: Ackerman

HW1: Emacs and Shell scripting

  • Keyboard shortcuts
  • Shell scripting
    • Syntax
      • Shebang ("#!/bin/bash")
      • if, else
      • Variable assignment
      • Arguments, special variables
      • Redirection
    • Programs/commands
      • ps
      • tr
      • diff, comm
      • awk
      • sed
      • find
      • cat
      • echo
      • touch
      • grep
    • Regex
      • POSIX Extended
      • grep -E
    • File systems stuff
      • Symlinks vs hardlinks
      • inodes

HW2: Python and elisp

  • Opening files
  • Data structures (list, dict, tuples, sets)
  • Coding (python and elisp)

HW3: React and testing

  • Components and rendering, states, sync and async
  • npm (package management), package.json, what to include in git
  • Network protocols and caching
  • Testing

HW4: Git Usage

  • Commands:
    • init, clone, pull, push
    • branch, add, commit, merge, reset, checkout

HW5: Git Internals, Topological Sort

  • trees, what is in each node
    • child -> parent
  • Ordering of dependencies

HW6: C and makefiles

  • valgrind: detect memory issues
  • gdb: breakpoints, watchpoints, backtrace, checkpoints, reverse continue
  • gcc flags
    • -g: add debugging info
    • -O: optimization (-O1, -O2, -O3, -Os)
    • -fsanitize:
    • -flto:
  • Makefiles:
    • syntax (target, dependencies, rules)
    • special variables ($@, $^)
    • When does make run a command: dependencies newer than target