/* Copyright 2016 Google Inc.

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License. */

/* Routines for debugging. */

#include "nsync_cpp.h"
#include "platform.h"
#include "compiler.h"
#include "cputype.h"
#include "nsync.h"
#include "dll.h"
#include "sem.h"
#include "wait_internal.h"
#include "common.h"
#include "atomic.h"

NSYNC_CPP_START_

/* ---------- */

/* An emit_buf represents a buffer into which debug information can
   be written.  */
struct emit_buf {
        char *start;  /* start of buffer */
        int len;      /* pength of buffer */
        int pos;      /* position of next character to bve written */
        int overflow; /* non-zero iff buffer overflow has occurred */
};

/* Initialize *b to point to start[0, .., len-1], and return b.
   of to an internal static buffer if buf==NULL. */
static struct emit_buf *emit_init (struct emit_buf *b, char *start, int len) {
        b->start = start;
        b->len = len;
        b->pos = 0;
        b->overflow = 0;
        return (b);
}


/* Write character c to buffer *b. */
static void emit_c (struct emit_buf *b, int c) {
        if (b->pos < b->len) {
                b->start[b->pos++] = c;
        } else if (!b->overflow) {
                static const char suffix[] = "...";
                const char *s = &suffix[sizeof (suffix)]; /* past nul */
                char *p = &b->start[b->len];  /* past end */
                while (s > suffix && p > b->start) {
                        *--p = *--s;
                }
                b->overflow = 1;
        }
}

/* A printf-like function that writes to an emit_buf.
   It understands only the format specifiers %s (const char *), and %i
   (uintptr_t in hex), with no modifiers. */
static void emit_print (struct emit_buf *b, const char *fmt, ...) {
        va_list ap;
        va_start (ap, fmt);
        while (*fmt != 0) {
                int c = *fmt++;
                if (c != '%') {
                        emit_c (b, c);
                } else {
                        c = *fmt++;
                        if (c == 's') {
                                const char *s = va_arg (ap, const char *);
                                while (*s != 0) {
                                        emit_c (b, *s++);
                                }
                        } else if (c == 'i') {
                                uintptr_t n = va_arg (ap, uintptr_t);
                                int i;
                                for (i = 0; (n >> i) >= 0x10; i += 4) {
                                }
                                for (; i >= 0; i -= 4) {
                                        emit_c (b, "0123456789abcdef"[(n >> i) & 0xf]);
                                }
                        } else {
                                ASSERT (0);
                        }
                }
        }
        va_end (ap);
}

/* Map a bit in a uint32_t to a human-readable name. */
struct bit_name {
        uint32_t mask;
        const char *name;
};

/* names for bits in a mu word */
static const struct bit_name mu_bit[] = {
        { MU_WLOCK,          "wlock" },
        { MU_SPINLOCK,       "spin" },
        { MU_WAITING,        "wait" },
        { MU_DESIG_WAKER,    "desig" },
        { MU_CONDITION,      "cond" },
        { MU_WRITER_WAITING, "writer" },
        { MU_LONG_WAIT,      "long" },
        { MU_ALL_FALSE,      "false" },
        { 0,                 "" }  /* sentinel */
};

/* names for bits in a cv word */
static const struct bit_name cv_bit[] = {
        { CV_SPINLOCK,       "spin" },
        { CV_NON_EMPTY,      "wait" },
        { 0,                 "" }  /* sentinel */
};

/* names for bits in a waiter flags word */
static const struct bit_name waiter_flags_bit[] = {
        { WAITER_RESERVED,   "rsrvd" },
        { WAITER_IN_USE,     "in_use" },
        { 0,                 "" }  /* sentinel */
};

/* Emit the names of bits in word to buffer *b using names[] */
static void emit_word (struct emit_buf *b, const struct bit_name *name, uint32_t word) {
      int i;
      for (i = 0; name[i].mask != 0; i++) {
              if ((word & name[i].mask) != 0) {
                      emit_print (b, " %s", name[i].name);
              }
      }
}

/* Emit the waiter queue *q to *b. */
static void emit_waiters (struct emit_buf *b, nsync_dll_list_ list) {
        nsync_dll_element_ *p = nsync_dll_first_ (list);
        nsync_dll_element_ *next;
        if (p != NULL) {
                emit_print (b, "\nwaiters =\n");
        }
        for (; p != NULL && !b->overflow; p = next) {
                struct nsync_waiter_s *nw = DLL_NSYNC_WAITER (p);
                waiter *w = DLL_WAITER (p);
                next = NULL;
                emit_print (b, "   %i", (uintptr_t) w);
                if (w->tag != WAITER_TAG) {
                        emit_print (b, "bad WAITER_TAG %i",
                                    (uintptr_t) w->tag);
                } else {
                        next = nsync_dll_next_ (list, p);
                        if (nw->tag != NSYNC_WAITER_TAG) {
                                emit_print (b, " bad WAITER_TAG %i",
                                            (uintptr_t) nw->tag);
                        } else {
                                emit_print (b, " embedded=%i waiting=%i",
                                            (uintptr_t) (w->flags & NSYNC_WAITER_FLAG_MUCV),
                                            (uintptr_t) ATM_LOAD (&nw->waiting));
                        }
                        emit_word (b, waiter_flags_bit, w->flags);
                        emit_print (b, " %s removes=%i cond=(%i %i %i)",
                                    w->l_type == nsync_writer_type_? "writer" :
                                    w->l_type == nsync_reader_type_? "reader" :
                                                                     "??????",
                                    (uintptr_t) ATM_LOAD (&w->remove_count),
                                    (uintptr_t) w->cond.f,
                                    (uintptr_t) w->cond.v,
                                    (uintptr_t) w->cond.eq);
                        if (w->same_condition.next != &w->same_condition) {
                                emit_print (b, " same_as %i",
                                            (uintptr_t) DLL_WAITER_SAMECOND (
                                                w->same_condition.next));
                        }
                }
                emit_c (b, '\n');
        }
}

/* Emit to *b the state of *mu, and return a pointer to *b's buffer.
  
   If blocking!=0, print_waiters!=0, and *mu's waiter list is non-empty, the
   call will block until it can acquire the spinlock.
   If print_waiters!=0, the waiter list is printed.
   The spinlock is released before return if it was acquired.
   blocking==0 && print_waiters!=0 is unsafe and is intended for use within
   interactive debuggers.  */
static char *emit_mu_state (struct emit_buf *b, nsync_mu *mu,
			    int blocking, int print_waiters) {
        uintptr_t word;
        uintptr_t readers;
        int acquired = 0;
        IGNORE_RACES_START ();
        word = ATM_LOAD (&mu->word);
        if ((word & MU_WAITING) != 0 && print_waiters &&  /* can benefit from lock */
	    (blocking || (word & MU_SPINLOCK) == 0)) {  /* willing, or no need to wait */
                word = nsync_spin_test_and_set_ (&mu->word, MU_SPINLOCK, MU_SPINLOCK, 0);
                acquired = 1;
        }
        readers = word / MU_RLOCK;
        emit_print (b, "mu 0x%i -> 0x%i = {", (uintptr_t) mu, word);
        emit_word (b, mu_bit, word);
        if (readers != 0) {
                emit_print (b, " readers=0x%i", readers);
        }
        emit_print (b, " }");
        if (print_waiters) {
                emit_waiters (b, mu->waiters);
        }
        if (acquired) {
                ATM_STORE_REL (&mu->word, word); /* release store */
        }
        emit_c (b, 0);
        IGNORE_RACES_END ();
        return (b->start);
}

/* Emit to *b the state of *cv, and return a pointer to *b's buffer.

   If blocking!=0, print_waiters!=0, and *cv's waiter list is non-empty, the
   call will block until it can acquire the spinlock.
   If print_waiters!=0, the waiter list is printed.
   The spinlock is released before return if it was acquired.
   blocking==0 && print_waiters!=0 is unsafe and is intended for use within
   interactive debuggers.  */
static char *emit_cv_state (struct emit_buf *b, nsync_cv *cv,
			    int blocking, int print_waiters) {
        uintptr_t word;
        int acquired = 0;
        IGNORE_RACES_START ();
        word = ATM_LOAD (&cv->word);
        if ((word & CV_NON_EMPTY) != 0 && print_waiters &&  /* can benefit from lock */
	    (blocking || (word & CV_SPINLOCK) == 0)) {  /* willing, or no need to wait */
                word = nsync_spin_test_and_set_ (&cv->word, CV_SPINLOCK, CV_SPINLOCK, 0);
                acquired = 1;
        }
        emit_print (b, "cv 0x%i -> 0x%i = {", (uintptr_t) cv, word);
        emit_word (b, cv_bit, word);
        emit_print (b, " }");
        if (print_waiters) {
                emit_waiters (b, cv->waiters);
        }
        if (acquired) {
                ATM_STORE_REL (&cv->word, word); /* release store */
        }
        emit_c (b, 0);
        IGNORE_RACES_END ();
        return (b->start);
}

char *nsync_mu_debug_state (nsync_mu *mu, char *buf, int n) {
        struct emit_buf b;
        return (emit_mu_state (emit_init (&b, buf, n), mu, 0, 0));
}

char *nsync_cv_debug_state (nsync_cv *cv, char *buf, int n) {
        struct emit_buf b;
        return (emit_cv_state (emit_init (&b, buf, n), cv, 0, 0));
}

char *nsync_mu_debug_state_and_waiters (nsync_mu *mu, char *buf, int n) {
        struct emit_buf b;
        return (emit_mu_state (emit_init (&b, buf, n), mu, 1, 1));
}

char *nsync_cv_debug_state_and_waiters (nsync_cv *cv, char *buf, int n) {
        struct emit_buf b;
        return (emit_cv_state (emit_init (&b, buf, n), cv, 1, 1));
}

static char nsync_debug_buf[1024];

char *nsync_mu_debugger (nsync_mu *mu) {
        struct emit_buf b;
        return (emit_mu_state (emit_init (&b, nsync_debug_buf,
                                          (int) sizeof (nsync_debug_buf)),
                               mu, 0, 1));
}
char *nsync_cv_debugger (nsync_cv *cv) {
        struct emit_buf b;
        return (emit_cv_state (emit_init (&b, nsync_debug_buf,
                                          (int) sizeof (nsync_debug_buf)),
                               cv, 0, 1));
}

NSYNC_CPP_END_