Merge pull request #185 from jaypipes/rand_str_var_len

Adds support for variable-length rand string

src/lua/internal/sysbench.rand.lua

@@ -32,6 +32,7 @@ uint32_t sb_rand_pareto(uint32_t, uint32_t);
 uint32_t sb_rand_zipfian(uint32_t, uint32_t);
 uint32_t sb_rand_unique(void);
 void sb_rand_str(const char *, char *);
+void sb_rand_varstr(char *, uint32_t, uint32_t);
 double sb_rand_uniform_double(void);
 ]]
 
@@ -74,6 +75,15 @@ function sysbench.rand.string(fmt)
    return ffi.string(buf, buflen)
 end
 
+function sysbench.rand.varstring(min_len, max_len)
+   assert(min_len <= max_len)
+   assert(max_len > 0)
+   local buflen = max_len
+   local buf = ffi.new("uint8_t[?]", buflen)
+   local nchars = ffi.C.sb_rand_varstr(buf, min_len, max_len)
+   return ffi.string(buf, nchars)
+end
+
 function sysbench.rand.uniform_double()
    return ffi.C.sb_rand_uniform_double()
 end

src/sb_rand.c

@@ -343,6 +343,32 @@ void sb_rand_str(const char *fmt, char *buf)
   }
 }
 
+/*
+  Generates a random string of ASCII characters between '0' and 'z' of a length
+  between min and max. buf should have enough room for max len bytes. Returns
+  the number of characters written into the buffer.
+ */
+
+uint32_t sb_rand_varstr(char *buf, uint32_t min_len, uint32_t max_len)
+{
+  unsigned int i;
+  uint32_t num_chars;
+  if (max_len == 0) {
+    return 0; /* we can't be sure buf is long enough to populate, so be safe */
+  }
+  if (min_len > max_len)
+  {
+    min_len = 1;
+  }
+
+  num_chars = sb_rand_uniform(min_len, max_len);
+  for (i=0; i < num_chars; i++)
+  {
+    buf[i] = sb_rand_uniform('0', 'z');
+  }
+  return num_chars;
+}
+
 /*
   Unique random sequence generator. This is based on public domain code from
   https://github.com/preshing/RandomSequence

src/sb_rand.h

@@ -71,5 +71,6 @@ uint32_t sb_rand_pareto(uint32_t, uint32_t);
 uint32_t sb_rand_zipfian(uint32_t, uint32_t);
 uint32_t sb_rand_unique(void);
 void sb_rand_str(const char *, char *);
+uint32_t sb_rand_varstr(char *, uint32_t, uint32_t);
 
 #endif /* SB_RAND_H */

tests/t/api_rand.t

@@ -7,8 +7,14 @@ PRNG Lua API tests
   $ cat >$CRAMTMP/api_rand.lua <<EOF
   > ffi.cdef[[int printf(const char *fmt, ...);]]
   > function init()
-  >   for k, v in pairs(sysbench.rand) do
-  >     print(string.format("sysbench.rand.%s", k))
+  >   -- Ensure a consistent sort order...
+  >   mod_funcs = {}
+  >   for f in pairs(sysbench.rand) do
+  >     table.insert(mod_funcs, f)
+  >   end
+  >   table.sort(mod_funcs)
+  >   for i, f in ipairs(mod_funcs) do
+  >     print(string.format("sysbench.rand.%s", f))
   >   end
   > end
   > function event()
@@ -16,6 +22,7 @@ PRNG Lua API tests
   >   print("sysbench.rand.unique(0, 4294967295) = " .. sysbench.rand.unique(0, 4294967295))
   >   ffi.C.printf("sysbench.rand.uniform_uint64() = %llu\n", sysbench.rand.uniform_uint64())
   >   print([[sysbench.rand.string("abc-###-@@@-xyz") = ]] .. sysbench.rand.string("abc-###-@@@-xyz"))
+  >   print([[sysbench.rand.varstring(1, 23) = ]] .. sysbench.rand.varstring(1, 23))
   >   print("sysbench.rand.uniform(0, 99) = " .. sysbench.rand.uniform(0, 99))
   >   print("sysbench.rand.gaussian(0, 99) = " .. sysbench.rand.gaussian(0, 99))
   >   print("sysbench.rand.special(0, 99) = " .. sysbench.rand.special(0, 99))
@@ -25,20 +32,22 @@ PRNG Lua API tests
   > EOF
 
   $ sysbench $SB_ARGS $CRAMTMP/api_rand.lua run
-  sysbench.rand.uniform
-  sysbench.rand.special
-  sysbench.rand.zipfian
-  sysbench.rand.unique
-  sysbench.rand.gaussian
-  sysbench.rand.uniform_uint64
-  sysbench.rand.uniform_double
-  sysbench.rand.pareto
-  sysbench.rand.string
   sysbench.rand.default
+  sysbench.rand.gaussian
+  sysbench.rand.pareto
+  sysbench.rand.special
+  sysbench.rand.string
+  sysbench.rand.uniform
+  sysbench.rand.uniform_double
+  sysbench.rand.uniform_uint64
+  sysbench.rand.unique
+  sysbench.rand.varstring
+  sysbench.rand.zipfian
   sysbench.rand.default\(0, 99\) = [0-9]{1,2} (re)
   sysbench.rand.unique\(0, 4294967295\) = [0-9]{1,10} (re)
   sysbench.rand.uniform_uint64\(\) = [0-9]+ (re)
   sysbench.rand.string\(".*"\) = abc-[0-9]{3}-[a-z]{3}-xyz (re)
+  sysbench.rand.varstring\(1, 23\) = [0-z]{1,23} (re)
   sysbench.rand.uniform\(0, 99\) = [0-9]{1,2} (re)
   sysbench.rand.gaussian\(0, 99\) = [0-9]{1,2} (re)
   sysbench.rand.special\(0, 99\) = [0-9]{1,2} (re)