feat(stdlib): rand/div/qsort/bsearch

include/stdlib.h

@@ -201,6 +201,172 @@ strtof(const char *restrict nptr, char **restrict endptr);
 long double
 strtold(const char *restrict nptr, char **restrict endptr);
 
+/* pseudo-random numbers, search, and integer arithmetic (todo 12) */
+
+/*
+ * C23 7.22.2/7.22.5/7.22.6: rand/srand, qsort/bsearch, the abs family, and
+ * the div family are ISO C core and present in every profile. The abs and
+ * div functions compute a pure function of their arguments, so they are
+ * declared const (the compiler folds and eliminates the calls in static
+ * links; GCC's own builtin declarations of abs/labs/llabs are const, and
+ * the attribute here matches them). rand and srand carry state, and
+ * qsort/bsearch call a caller-supplied comparator, so none of those four
+ * carries an intent attribute.
+ */
+
+/*
+ * The largest value rand() returns: 2^31 - 1, the largest int.
+ */
+#define RAND_MAX 2147483647
+
+/*
+ * Quotient/remainder pair from div/ldiv/lldiv: quot is the algebraic
+ * quotient truncated toward zero, rem the remainder of the same sign as
+ * the dividend, and quot*denom + rem == num.
+ */
+typedef struct
+{
+    int quot;
+    int rem;
+} div_t;
+
+typedef struct
+{
+    long quot;
+    long rem;
+} ldiv_t;
+
+typedef struct
+{
+    long long quot;
+    long long rem;
+} lldiv_t;
+
+/*
+ * Absolute value of n. The most-negative value returns itself: the
+ * negation happens in the unsigned type, which wraps, so the result is
+ * never undefined behavior and errno is never set.
+ */
+__attribute__((const)) int
+abs(int n);
+
+__attribute__((const)) long
+labs(long n);
+
+__attribute__((const)) long long
+llabs(long long n);
+
+/*
+ * Quotient and remainder of num/denom, truncated toward zero.
+ */
+__attribute__((const)) div_t
+div(int num, int denom);
+
+__attribute__((const)) ldiv_t
+ldiv(long num, long denom);
+
+__attribute__((const)) lldiv_t
+lldiv(long long num, long long denom);
+
+/*
+ * Pseudo-random integer in [0, RAND_MAX], deterministic for a given
+ * srand seed.
+ */
+int
+rand(void);
+
+/*
+ * Seed the rand() sequence with seed.
+ */
+void
+srand(unsigned int seed);
+
+/*
+ * Sort the array of nmemb elements of size bytes at base into ascending
+ * order according to compar (C23 7.22.5.2). compar receives two pointers
+ * to distinct elements and returns negative/zero/positive. The sort is
+ * not stable.
+ */
+void
+qsort(void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *));
+
+/*
+ * Binary-search the array of nmemb sorted elements of size bytes at base
+ * for *key, calling compar(key, element) (C23 7.22.5.1). Returns a
+ * pointer to the matching element, or NULL when there is none.
+ */
+void *
+bsearch(const void *key, const void *base, size_t nmemb, size_t size,
+        int (*compar)(const void *, const void *));
+
+#if VLIBC_LEVEL_GE(2)
+/* Level 2 (muslmimic): XSI and obsolescent extensions. */
+
+/*
+ * Reentrant rand: the state lives in the caller's *seedp, which is
+ * updated on every call, so the sequence is independent of rand()'s own
+ * global state.
+ */
+int
+rand_r(unsigned int *seedp);
+
+/*
+ * random/srandom family (XSI): a 31-bit pseudo-random sequence in
+ * [0, 2^31). initstate installs state (size bytes, at least
+ * sizeof(long)) as the current state buffer, seeds it, and returns the
+ * previous buffer; setstate installs the buffer and returns the previous
+ * one. srandom reseeds the current buffer.
+ */
+long
+random(void);
+
+void
+srandom(unsigned int seed);
+
+char *
+initstate(unsigned int seed, char *state, size_t size);
+
+char *
+setstate(char *state);
+
+/*
+ * drand48 family (XSI): a 48-bit linear congruential sequence carried in
+ * three unsigned shorts, least-significant first. drand48/erand48 return
+ * the current value divided by 2^48 as a double in [0, 1); lrand48/
+ * nrand48 return the high 31 bits; mrand48/jrand48 the high 32 bits
+ * sign-extended. The erand48/nrand48/jrand48 forms step the caller's
+ * xsubi in place; srand48/seed48/lcong48 manage the shared state and the
+ * multiplier/addend.
+ */
+double
+drand48(void);
+
+double
+erand48(unsigned short xsubi[3]);
+
+long
+lrand48(void);
+
+long
+nrand48(unsigned short xsubi[3]);
+
+long
+mrand48(void);
+
+long
+jrand48(unsigned short xsubi[3]);
+
+void
+srand48(long seedval);
+
+unsigned short *
+seed48(unsigned short seed16v[3]);
+
+void
+lcong48(unsigned short param[7]);
+
+#endif /* VLIBC_LEVEL_GE(2) */
+
 #ifdef __cplusplus
 }
 #endif