user: What is the c source code of the assembly code below?

```asm
<levenshtein>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbx
  sub    $0x28,%rsp
  mov    %rdi,-0x48(%rbp)
  mov    %rdx,%rbx
  mov    %fs:0x28,%rax
  mov    %rax,-0x38(%rbp)
  xor    %eax,%eax
  mov    (%rdx),%rdi
  call   <sqlite3_value_text@plt>
  mov    %rax,%r12
  mov    0x8(%rbx),%rdi
  call   <sqlite3_value_text@plt>
  test   %r12,%r12
  je     L21
  mov    %rax,%r13
  test   %rax,%rax
  je     L21
  mov    %rsp,-0x50(%rbp)
  mov    %r12,%rdi
  call   <strlen@plt>
  mov    %eax,%ebx
  mov    %r13,%rdi
  call   <strlen@plt>
  mov    %eax,%r14d
  lea    0x1(%rbx),%r11d
  lea    0x1(%rax),%eax
  imul   %r11,%rax
  lea    0xf(,%rax,4),%rax
  mov    %rax,%rcx
  and    $0xfffffffffffffff0,%rcx
  and    $0xfffffffffffff000,%rax
  mov    %rsp,%rdx
  sub    %rax,%rdx
L175:
  cmp    %rdx,%rsp
  je     L124
  sub    $0x1000,%rsp
  orq    $0x0,0xff8(%rsp)
  jmp    L175
L21:
  mov    -0x48(%rbp),%rdi
  call   <sqlite3_result_null@plt>
L55:
  mov    -0x38(%rbp),%rax
  sub    %fs:0x28,%rax
  jne    L171
  lea    -0x28(%rbp),%rsp
  pop    %rbx
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  pop    %rbp
  ret
L124:
  mov    %rcx,%rax
  and    $0xfff,%eax
  sub    %rax,%rsp
  test   %rax,%rax
  je     L191
  orq    $0x0,-0x8(%rsp,%rax,1)
L191:
  lea    0x3(%rsp),%rdi
  mov    %rdi,%rax
  shr    $0x2,%rax
  and    $0xfffffffffffffffc,%rdi
  movl   $0x0,0x0(,%rax,4)
  test   %r14d,%r14d
  je     L44
  mov    $0x1,%eax
L60:
  mov    %eax,%edx
  imul   %r11,%rdx
  lea    -0x1(%rax),%ecx
  imul   %r11,%rcx
  mov    (%rdi,%rcx,4),%ecx
  add    $0x1,%ecx
  mov    %ecx,(%rdi,%rdx,4)
  add    $0x1,%eax
  cmp    %eax,%r14d
  jae    L60
  test   %ebx,%ebx
  je     L73
L32:
  mov    $0x1,%eax
L125:
  mov    %eax,%ecx
  lea    -0x1(%rax),%edx
  mov    (%rdi,%rdx,4),%edx
  add    $0x1,%edx
  mov    %edx,(%rdi,%rcx,4)
  add    $0x1,%eax
  cmp    %eax,%ebx
  jae    L125
  test   %r14d,%r14d
  je     L133
L73:
  mov    %r13,%r10
  mov    $0x0,%r15d
  mov    $0x1,%r13d
  jmp    L172
L159:
  mov    %eax,%r9d
  movzbl (%r10),%eax
  cmp    %al,(%r12,%r9,1)
  setne  %al
  movzbl %al,%eax
  add    %rsi,%r9
  add    (%rdi,%r9,4),%eax
  cmp    %r8d,%eax
  cmova  %r8d,%eax
L142:
  mov    %edx,%r8d
  add    %rcx,%r8
  mov    %eax,(%rdi,%r8,4)
  add    $0x1,%edx
  cmp    %edx,%ebx
  jb     L188
L49:
  mov    %edx,%eax
  add    %rsi,%rax
  mov    (%rdi,%rax,4),%r9d
  add    $0x1,%r9d
  lea    -0x1(%rdx),%eax
  mov    %eax,%r8d
  add    %rcx,%r8
  mov    (%rdi,%r8,4),%r8d
  add    $0x1,%r8d
  cmp    %r8d,%r9d
  jae    L159
  mov    %eax,%r8d
  movzbl (%r10),%eax
  cmp    %al,(%r12,%r8,1)
  setne  %al
  movzbl %al,%eax
  add    %rsi,%r8
  add    (%rdi,%r8,4),%eax
  cmp    %r9d,%eax
  cmova  %r9d,%eax
  jmp    L142
L188:
  add    $0x1,%r13d
  add    $0x1,%r15d
  add    $0x1,%r10
  cmp    %r13d,%r14d
  jb     L133
L172:
  mov    $0x1,%edx
  test   %ebx,%ebx
  je     L188
  mov    %r15d,%esi
  imul   %r11,%rsi
  mov    %r13d,%ecx
  imul   %r11,%rcx
  jmp    L49
L44:
  test   %ebx,%ebx
  jne    L32
L133:
  mov    %ebx,%eax
  mov    %r14d,%r14d
  imul   %r11,%r14
  add    %r14,%rax
  mov    (%rdi,%rax,4),%esi
  mov    -0x48(%rbp),%rdi
  call   <sqlite3_result_int@plt>
  mov    -0x50(%rbp),%rsp
  jmp    L55
L171:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
extern void levenshtein(sqlite3_context *context, int argc, sqlite3_value **argv) {
  char *s1;
  char *s2;
  s1 = (char *)sqlite3_value_text(argv[0]);
  s2 = (char *)sqlite3_value_text(argv[1]);
  if ((s1 == NULL) || (s2 == NULL)) {
    sqlite3_result_null(context);
  } else {
    unsigned int x;
    unsigned int y;
    unsigned int s1len;
    unsigned int s2len;
    s1len = strlen(s1);
    s2len = strlen(s2);
    unsigned int matrix[s2len + 1][s1len + 1];
    matrix[0][0] = 0;
    for (x = 1; x <= s2len; x++) {
      matrix[x][0] = matrix[x - 1][0] + 1;
    }
    for (y = 1; y <= s1len; y++) {
      matrix[0][y] = matrix[0][y - 1] + 1;
    }
    for (x = 1; x <= s2len; x++) {
      for (y = 1; y <= s1len; y++) {
        matrix[x][y] = ((matrix[x - 1][y] + 1) < (matrix[x][y - 1] + 1) ? ((matrix[x - 1][y] + 1) < (matrix[x - 1][y - 1] + (s1[y - 1] == s2[x - 1] ? 0 : 1)) ? (matrix[x - 1][y] + 1) : (matrix[x - 1][y - 1] + (s1[y - 1] == s2[x - 1] ? 0 : 1))) : ((matrix[x][y - 1] + 1) < (matrix[x - 1][y - 1] + (s1[y - 1] == s2[x - 1] ? 0 : 1)) ? (matrix[x][y - 1] + 1) : (matrix[x - 1][y - 1] + (s1[y - 1] == s2[x - 1] ? 0 : 1))));
      }
    }
    sqlite3_result_int(context, (int)matrix[s2len][s1len]);
  }
}
```