sysprof/sfile.c

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- */

/* Sysprof -- Sampling, systemwide CPU profiler
 * Copyright 2004, Red Hat, Inc.
 * Copyright 2004, 2005, Soeren Sandmann
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <glib.h>
#if 0
#include <bzlib.h>
#endif
#include "sfile.h"
#include "sformat.h"
#include <sys/mman.h>

typedef struct BuildContext BuildContext;
typedef struct Instruction Instruction;
typedef enum
{
    BEGIN, END, VALUE
} InstructionKind;

struct Instruction
{
    InstructionKind kind;
    SType *type;
    
    union
    {
        struct
        {
            int n_elements;
            int id;
            Instruction *end_instruction;
        } begin;
	
        struct
        {
            Instruction *begin_instruction;
            gpointer object;
        } end;
	
        struct
        {
            int target_id;
            Instruction *target_instruction;
            gpointer target_object;
            gpointer *location;
        } pointer;
	
        struct
        {
            int value;
        } integer;
	
        struct
        {
            char *value;
        } string;
    } u; 
};

struct BuildContext
{
    SContext *context;
    
    GArray *instructions;
};

static void
set_error (GError **err,
	   gint code,
	   const char *format,
	   va_list args)
{
    char *msg;
    
    if (!err)
        return;
    
    msg = g_strdup_vprintf (format, args);
    
    if (*err == NULL)
    {
        *err = g_error_new_literal (G_MARKUP_ERROR, code, msg);
    }
    else
    {
        /* Warning text from GLib */
        g_warning ("GError set over the top of a previous GError or uninitialized memory.\n" 
                   "This indicates a bug in someone's code. You must ensure an error is NULL before it's set.\n"
                   "The overwriting error message was: %s",
                   msg);
    }
    
    g_free (msg);
}

static void
set_unknown_element_error (GError **err, const char *format, ...)
{
    va_list args;
    va_start (args, format);
    set_error (err, G_MARKUP_ERROR_UNKNOWN_ELEMENT, format, args);
    va_end (args);
}

static void
set_unknown_attribute_error (GError **err, const char *format, ...)
{
    va_list args;
    va_start (args, format);
    set_error (err, G_MARKUP_ERROR_UNKNOWN_ATTRIBUTE, format, args);
    va_end (args);
}

static void
set_invalid_content_error (GError **err, const char *format, ...)
{
    va_list args;
    va_start (args, format);
    set_error (err, G_MARKUP_ERROR_INVALID_CONTENT, format, args);
    va_end (args);
}

/* reading */
static gboolean
is_all_blank (const char *text)
{
    while (g_ascii_isspace (*text))
	text++;
    
    return (*text == '\0');
}

static gboolean
get_number (const char *text, int *number)
{
    char *end;
    int result;
    gboolean retval;
    
    result = strtol (text, &end, 10);
    
    retval = is_all_blank (end);
    
    if (retval && number)
        *number = result;
    
    return retval;
}

struct SFileInput
{
    int n_instructions;
    Instruction *instructions;
    Instruction *current_instruction;
    GHashTable *instructions_by_location;
};

static gboolean
check_name (Instruction *instr,
	    const char *name)
{
    const char *type_name = stype_get_name (instr->type);

    return strcmp (name, type_name) == 0;
}

void
sfile_begin_get_record (SFileInput *file, const char *name)
{
    Instruction *instruction = file->current_instruction++;
    
    g_return_if_fail (instruction->kind == BEGIN);
    g_return_if_fail (check_name (instruction, name));
    g_return_if_fail (stype_is_record (instruction->type));
}

int
sfile_begin_get_list   (SFileInput       *file,
                        const char   *name)
{
    Instruction *instruction = file->current_instruction++;
    
    g_return_val_if_fail (instruction->kind == BEGIN, 0);
    g_return_val_if_fail (check_name (instruction, name), 0);
    g_return_val_if_fail (stype_is_list (instruction->type), 0);
    
    return instruction->u.begin.n_elements;
}

void
sfile_get_pointer (SFileInput  *file,
                   const char *name,
                   gpointer    *location)
{
    Instruction *instruction;
    
    instruction = file->current_instruction++;
    g_return_if_fail (stype_is_pointer (instruction->type));
     
   instruction->u.pointer.location = location;
    
    *location = (gpointer) 0xFedeAbe;
    
    if (location)
    {
        if (g_hash_table_lookup (file->instructions_by_location, location))
            g_warning ("Reading into the same location twice\n");
	
        g_hash_table_insert (file->instructions_by_location, location, instruction);
    }
 }

void
sfile_get_integer (SFileInput  *file,
		   const char  *name,
		   gint32      *integer)
{
    Instruction *instruction;

    instruction = file->current_instruction++;
    g_return_if_fail (stype_is_integer (instruction->type));
    
    if (integer)
        *integer = instruction->u.integer.value;
}

void
sfile_get_string (SFileInput  *file,
		  const char  *name,
		  char       **string)
{
    Instruction *instruction;
    
    instruction = file->current_instruction++;
    g_return_if_fail (stype_is_string (instruction->type));
    
    if (string)
        *string = g_strdup (instruction->u.string.value);
}

static void
hook_up_pointers (SFileInput *file)
{
    int i;
    
    for (i = 0; i < file->n_instructions; ++i)
    {
        Instruction *instruction = &(file->instructions[i]);
	
        if (stype_is_pointer (instruction->type))
        {
            gpointer target_object;
            Instruction *target_instruction;
	    
            target_instruction = instruction->u.pointer.target_instruction;
	    
            if (target_instruction)
                target_object = target_instruction->u.begin.end_instruction->u.end.object;
            else
                target_object = NULL;
	    
            *(instruction->u.pointer.location) = target_object;
        }
    }
}

void
sfile_end_get          (SFileInput  *file,
                        const char  *name,
                        gpointer     object)
{
    Instruction *instruction = file->current_instruction++;
    
    g_return_if_fail (instruction->kind == END);
    g_return_if_fail (check_name (instruction, name));
    
    instruction->u.end.object = object;
    
    if (file->current_instruction == file->instructions + file->n_instructions)
        hook_up_pointers (file);
}

static int
get_id (const char **names, const char **values, GError **err)
{
    const char *id_string = NULL;
    int id, i;
    
    for (i = 0; names[i] != NULL; ++i)
    {
	if (strcmp (names[i], "id") != 0)
	{
            set_unknown_attribute_error (err, "Unknown attribute: %s", names[i]);
	    return -1;
	}
	
        if (id_string)
        {
            set_invalid_content_error (err, "Attribute 'id' defined twice");
            return -1;
        }
	
        id_string = values[i];
    }
    
    if (!id_string)
        return 0;
    
    if (!get_number (id_string, &id) || id < 1)
    {
        set_invalid_content_error (err, "Bad attribute value for attribute 'id' (must be >= 1)\n");
        return -1;
    }
    
    return id;
}

static void
handle_begin_element (GMarkupParseContext *parse_context,
		      const gchar *element_name,
		      const gchar **attribute_names,
		      const gchar **attribute_values,
		      gpointer user_data,
		      GError **err)
{
    BuildContext *build = user_data;
    Instruction instruction;
    
    instruction.u.begin.id = get_id (attribute_names, attribute_values, err);
    
    if (instruction.u.begin.id == -1)
        return;
    
    instruction.type = scontext_begin (build->context, element_name);
    if (!instruction.type)
    {
        set_unknown_element_error (err, "<%s> unexpected here", element_name);
        return;
    }

    if (stype_is_list (instruction.type) || stype_is_record (instruction.type))
    {
	instruction.kind = BEGIN;
	g_array_append_val (build->instructions, instruction);
    }
}

static void
handle_end_element (GMarkupParseContext *context,
		    const gchar *element_name,
		    gpointer user_data,
		    GError **err)
{
    BuildContext *build = user_data;
    Instruction instruction;
    
    instruction.type = scontext_end (build->context, element_name);
    if (!instruction.type)
    {
        set_unknown_element_error (err, "</%s> unexpected here", element_name);
        return;
    }
    
    if (stype_is_list (instruction.type) || stype_is_record (instruction.type))
    {
	instruction.kind = END;
    
	g_array_append_val (build->instructions, instruction);
    }
}

static gboolean
decode_text (const char *text, char **decoded)
{
    int length = strlen (text);
    
    if (length < 2)
        return FALSE;
    
    if (text[0] != '\"' || text[length - 1] != '\"')
        return FALSE;
    
    if (decoded)
        *decoded = g_strndup (text + 1, length - 2);
    
    return TRUE;
}

static const char *
skip_whitespace (const char *text)
{
    while (g_ascii_isspace (*text))
	text++;
    
    return text;
}

static void
handle_text (GMarkupParseContext *context,
	     const gchar *text,
             gsize text_len,
	     gpointer user_data,
	     GError **err)
{
    BuildContext *build = user_data;
    Instruction instruction;
    
    if (*text == '\0')
	return;
    
    text = skip_whitespace (text);
    if (*text == '\0')
	return;
    
    instruction.type = scontext_text (build->context);
    if (!instruction.type)
    {
	/* FIXME: what are line and ch used for here? */
        int line, ch;
        g_markup_parse_context_get_position (context, &line, &ch);
        set_invalid_content_error (err, "Unexpected text data");
        return;
    }
    
    instruction.kind = VALUE;
    
    if (stype_is_pointer (instruction.type))
    {
        if (!get_number (text, &instruction.u.pointer.target_id))
        {
            set_invalid_content_error (err, "Content '%s' of pointer element is not a number", text);
	    return;
        }
    }
    else if (stype_is_integer (instruction.type))
    {
        if (!get_number (text, &instruction.u.integer.value))
        {
            set_invalid_content_error (err, "Content '%s' of integer element is not a number", text);
            return;
        }
    }
    else if (stype_is_string (instruction.type))
    {
        if (!decode_text (text, &instruction.u.string.value))
        {
            set_invalid_content_error (err, "Content '%s' of text element is ill-formed", text);
	    return;
        }
    }
    else
    {
	g_assert_not_reached();
    }
    
    g_array_append_val (build->instructions, instruction);
}

static void
free_instructions (Instruction *instructions, int n_instructions)
{
    int i;
    
    for (i = 0; i < n_instructions; ++i)
    {
        Instruction *instruction = &(instructions[i]);
	
        if (stype_is_string (instruction->type))
            g_free (instruction->u.string.value);
    }
    
    g_free (instructions);
}

/* This functions makes end instructions point to the corresponding
 * begin instructions, and counts the number of instructions
 * contained in a begin/end pair
 */
static Instruction *
process_instruction_pairs (Instruction *first)
{
    Instruction *instruction;
    int n_elements;
    
    g_assert (first->kind == BEGIN);
    
    instruction = first + 1;
    
    n_elements = 0;
    while (instruction->kind != END)
    {
        if (instruction->kind == BEGIN)
        {
            instruction = process_instruction_pairs (instruction);
            if (!instruction)
                return NULL;
        }
        else
        {
            instruction++;
        }
	
        n_elements++;
    }
    
    first->u.begin.n_elements = n_elements;
    first->u.begin.end_instruction = instruction;
    
    instruction->u.end.begin_instruction = first;
    
    return instruction + 1;
}

static gboolean
post_process_read_instructions (Instruction  *instructions,
				int           n_instructions,
				GError      **err)
{
    gboolean retval = TRUE;
    GHashTable *instructions_by_id;
    int i;
    
    /* count list instructions, check pointers */
    process_instruction_pairs (instructions);
    
    /* Build id->instruction map */
    instructions_by_id = g_hash_table_new (g_direct_hash, g_direct_equal);
    for (i = 0; i < n_instructions; ++i)
    {
        Instruction *instruction = &(instructions[i]);
	
        if (instruction->kind == BEGIN)
        {
            int id = instruction->u.begin.id;
	    
            if (id)
                g_hash_table_insert (instructions_by_id, GINT_TO_POINTER (id), instruction);
        }
    }
    
    /* Make pointer instructions point to the corresponding element */
    for (i = 0; i < n_instructions; ++i)
    {
        Instruction *instruction = &(instructions[i]);
	
        if (stype_is_pointer (instruction->type))
        {
            int target_id = instruction->u.pointer.target_id;
	    
            if (target_id)
            {
                Instruction *target = g_hash_table_lookup (instructions_by_id,
                                                           GINT_TO_POINTER (target_id));
		
                if (target)
                {
		    if (stype_get_target_type (instruction->type) == target->type)
		    {
			instruction->u.pointer.target_instruction = target;
		    }
		    else
		    {
			set_invalid_content_error (err, "Id %d references an element of the wrong type",
						   instruction->u.pointer.target_id);
			retval = FALSE;
			break;
		    }
                }
                else
                {
                    set_invalid_content_error (err, "Id %d doesn't reference any record or list",
                                               instruction->u.pointer.target_id);
                    retval = FALSE;
                    break;
                }
            }
            else
            {
                instruction->u.pointer.target_instruction = NULL;
            }
        }
    }
    
    g_hash_table_destroy (instructions_by_id);
    
    return retval;
}

static Instruction *
build_instructions (const char *contents,
                    gsize       length,
		    SFormat    *format,
		    int        *n_instructions,
		    GError    **err)
{
    BuildContext build;
    GMarkupParseContext *parse_context;
    
    GMarkupParser parser = {
	handle_begin_element,
	handle_end_element,
	handle_text,
	NULL, /* passthrough */
	NULL, /* error */
    };
    
    build.context = scontext_new (format);
    build.instructions = g_array_new (TRUE, TRUE, sizeof (Instruction));
    
    parse_context = g_markup_parse_context_new (&parser, 0, &build, NULL);

    while (length)
    {
        int bytes = MIN (length, 65536);

        if (!g_markup_parse_context_parse (parse_context, contents, bytes, err))
        {
            free_instructions ((Instruction *)build.instructions->data, build.instructions->len);
            return NULL;
        }

        contents += bytes;
        length -= bytes;
    }
    
    if (!g_markup_parse_context_end_parse (parse_context, err))
    {
        free_instructions ((Instruction *)build.instructions->data, build.instructions->len);
        return NULL;
    }
    
    if (!scontext_is_finished (build.context))
    {
        set_invalid_content_error (err, "Premature end of file\n");
	
        free_instructions ((Instruction *)build.instructions->data, build.instructions->len);
        return NULL;
    }
    
    if (!post_process_read_instructions ((Instruction *)build.instructions->data,
                                         build.instructions->len, err))
    {
        free_instructions ((Instruction *)build.instructions->data, build.instructions->len);
        return NULL;
    }

    *n_instructions = build.instructions->len;

    return (Instruction *)g_array_free (build.instructions, FALSE);
}

SFileInput *
sfile_load (const char  *filename,
	    SFormat       *format,
	    GError     **err)
{
    gchar *contents;
    gsize length;
    SFileInput *input;
    GMappedFile *file;

    file = g_mapped_file_new (filename, FALSE, err);
    if (!file)
        return NULL;

    contents = g_mapped_file_get_contents (file);
    length = g_mapped_file_get_length (file);

    madvise (contents, length, MADV_SEQUENTIAL);
    
    input = g_new (SFileInput, 1);
    
    input->instructions = build_instructions (contents, length, format, &input->n_instructions, err);
    
    if (!input->instructions)
    {
        g_free (input);
        g_mapped_file_free (file);
        return NULL;
    }

    g_mapped_file_free (file);
    
    input->current_instruction = input->instructions;
    input->instructions_by_location = g_hash_table_new (g_direct_hash, g_direct_equal);
    
    return input;
}

/* Writing */
struct SFileOutput
{
    SFormat *format;
    GArray *instructions;
    GHashTable *objects;
    SContext *context;
};

SFileOutput *
sfile_output_new (SFormat       *format)
{
    SFileOutput *output = g_new (SFileOutput, 1);
    
    output->format = format;
    output->instructions = g_array_new (TRUE, TRUE, sizeof (Instruction));
    output->context = scontext_new (format);
    output->objects = g_hash_table_new (g_direct_hash, g_direct_equal);
    
    return output;
}

void
sfile_begin_add_record (SFileOutput       *file,
                        const char        *name)
{
    Instruction instruction;
    
    instruction.type = scontext_begin (file->context, name);
    
    g_return_if_fail (instruction.type);
    g_return_if_fail (stype_is_record (instruction.type));
    
    instruction.kind = BEGIN;    
    
    g_array_append_val (file->instructions, instruction);
}

void
sfile_begin_add_list   (SFileOutput *file,
                        const char  *name)
{
    Instruction instruction;
    
    instruction.type = scontext_begin (file->context, name);
    
    g_return_if_fail (instruction.type);
    g_return_if_fail (stype_is_list (instruction.type));
    
    instruction.kind = BEGIN;
    
    g_array_append_val (file->instructions, instruction);
}

void
sfile_end_add (SFileOutput       *file,
               const char        *name,
               gpointer           object)
{
    Instruction instruction;
    
    if (object && g_hash_table_lookup (file->objects, object))
    {
        g_warning ("Adding the same object (%p) twice", object);
        return;
    }
    
    instruction.type = scontext_end (file->context, name);
    
    if (!instruction.type)
    {
        g_warning ("invalid call of sfile_end_add()");
        return;
    }
    
    instruction.kind = END;
    instruction.u.end.object = object;
    
    g_array_append_val (file->instructions, instruction);
    
    if (object)
        g_hash_table_insert (file->objects, object, object);
}

static SType *
sfile_check_value (SFileOutput *file,
                   const char *name)
{
    SType *tmp_type;
    
    tmp_type = scontext_begin (file->context, name);
    if (!tmp_type)
	return NULL;
    
    tmp_type = scontext_text (file->context);
    if (!tmp_type)
	return NULL;
    
    tmp_type = scontext_end (file->context, name);
    if (!tmp_type)
	return NULL;
    
    return tmp_type;
}

void
sfile_add_string (SFileOutput *file,
		  const char  *name,
		  const char  *string)
{
    Instruction instruction;
    
    g_return_if_fail (g_utf8_validate (string, -1, NULL));
    
    instruction.type = sfile_check_value (file, name);
    if (!instruction.type || !stype_is_string (instruction.type))
    {
	g_warning ("Invalid call to sfile_add_string()");
	return;
    }
    instruction.kind = VALUE;
    instruction.u.string.value = g_strdup (string);
    
    g_array_append_val (file->instructions, instruction);
}

void
sfile_add_integer (SFileOutput *file,
                   const char  *name,
                   int          integer)
{
    Instruction instruction;
    
    instruction.type = sfile_check_value (file, name);
    if (!instruction.type || !stype_is_integer (instruction.type))
    {
	g_warning ("Invalid call to sfile_add_integer()");
	return;
    }
    instruction.kind = VALUE;
    instruction.u.integer.value = integer;
    
    g_array_append_val (file->instructions, instruction);
}

void
sfile_add_pointer (SFileOutput *file,
		   const char  *name,
		   gpointer     pointer)
{
    Instruction instruction;
    
    instruction.type = sfile_check_value (file, name);
    if (!instruction.type || !stype_is_pointer (instruction.type))
    {
	g_warning ("Invalid call to sfile_add_pointer()");
	return;
    }
    instruction.kind = VALUE;
    instruction.u.pointer.target_object = pointer;
    
    g_array_append_val (file->instructions, instruction);
}

static void
post_process_write_instructions (SFileOutput *sfile)
{
    int i;
    Instruction *instructions = (Instruction *)sfile->instructions->data;
    int n_instructions = sfile->instructions->len;
    int id;
    GHashTable *instructions_by_object;
    
    process_instruction_pairs (instructions);
    
    /* Set all id's to -1 and create map from objects to instructions */
    
    instructions_by_object = g_hash_table_new (g_direct_hash, g_direct_equal);
    
    for (i = 0; i < n_instructions; ++i)
    {
        Instruction *instruction = &(instructions[i]);
	
        if (instruction->kind == BEGIN)
        {
            instruction->u.begin.id = -1;
        }
        else if (instruction->kind == END && instruction->u.end.object)
        {
            g_hash_table_insert (instructions_by_object,
                                 instruction->u.end.object, instruction);
        }
    }
    
    /* Assign an id to all pointed-to instructions */
    id = 1;
    for (i = 0; i < n_instructions; ++i)
    {
        Instruction *instruction = &(instructions[i]);
	
        if (stype_is_pointer (instruction->type))
        {
            if (instruction->u.pointer.target_object)
            {
                Instruction *target;
		
                target =
                    g_hash_table_lookup (instructions_by_object,
                                         instruction->u.pointer.target_object);
		
                if (!target)
                {
                    g_warning ("pointer has unknown target\n");
		    goto out;
                }
		
                g_assert (target->kind == END);
		
                if (target->u.end.begin_instruction->u.begin.id == -1)
                    target->u.end.begin_instruction->u.begin.id = id++;
		
                instruction->u.pointer.target_id = 
                    target->u.end.begin_instruction->u.begin.id;
            }
            else
            {
                instruction->u.pointer.target_id = 0;
            }
        }
    }

out:
    g_hash_table_destroy (instructions_by_object);
}

static void
add_indent (GString *output,
	    int      indent)
{
    int i;
    
    for (i = 0; i < indent; ++i)
        g_string_append_c (output, ' ');
}

static void
add_integer (GString *output,
	     int      value)
{
    g_string_append_printf (output, "%d", value);
}

static void
add_string (GString    *output,
	    const char *str)
{
    char *escaped = g_markup_escape_text (str, -1);
    g_string_append_c (output, '\"');
    g_string_append (output, escaped);
    g_string_append_c (output, '\"');
    g_free (escaped);
}

static void
add_begin_tag (GString    *output,
	       int         indent,
	       const char *name,
	       int         id)
{
    add_indent (output, indent);
    
    if (id != -1)
        g_string_append_printf (output, "<%s id=\"%d\">", name, id);
    else
        g_string_append_printf (output, "<%s>", name);
}

static void
add_end_tag (GString    *output,
	     int         indent,
	     const char *name)
{
    add_indent (output, indent);
    g_string_append_printf (output, "</%s>", name);
}

static void
add_nl (GString *output)
{
    g_string_append_c (output, '\n');
}

#if 0
static void
disaster (int status)
{
    const char *error;
    switch (status)
    {
    case BZ_PARAM_ERROR:
	error = "BZ_PARAM_ERROR";
	break;
	
    case BZ_MEM_ERROR:
	error = "BZ_MEM_ERROR";
	break;
	
    case BZ_OUTBUFF_FULL:
	error = "BZ_OUTBUFF_FULL";
	break;
	
    default:
	error = "Unknown error";
	break;
    }
    
    g_error ("Failed to compress file: %s\n", error);
}

static void
bz2_compress (const guchar *input, int input_length,
	      guchar **output, int *output_length)
{
    size_t compressed_size;
    guchar *compressed_data;
    int status;
    
    g_return_if_fail (input != NULL);
    
    /* The bzip2 manual says:
     *
     * To guarantee that the compressed data will fit in its buffer,
     * allocate an output buffer of size 1% larger than the uncompressed
     * data, plus six hundred extra bytes.
     */
    compressed_size = (size_t)(1.02 * input_length + 600);
    compressed_data = g_malloc (compressed_size);
    
    status = BZ2_bzBuffToBuffCompress (compressed_data, &compressed_size,
                                       (guchar *)input, input_length,
                                       9 /* block size */,
                                       0 /* verbosity */,
                                       0 /* workfactor */);
    
    if (status != BZ_OK)
	disaster (status);
    
    if (output)
	*output = compressed_data;
    else
	g_free (compressed_data);
    
    if (output_length)
	*output_length = compressed_size;
}
#endif

static const char *
get_name (Instruction *inst)
{
    return stype_get_name (inst->type);
}

gboolean
sfile_output_save (SFileOutput  *sfile,
                   const char   *filename,
                   GError      **err)
{
    int i;
    Instruction *instructions;
    GString *output;
    int indent;
    gboolean retval;
#if 0
    guchar *compressed;
    size_t compressed_size;
#endif
    
    g_return_val_if_fail (sfile != NULL, FALSE);
    
    instructions = (Instruction *)sfile->instructions->data;
    
    post_process_write_instructions (sfile);
    
    indent = 0;
    output = g_string_new ("");
    for (i = 0; i < sfile->instructions->len; ++i)
    {
        Instruction *instruction = &(instructions[i]);
	
        switch (instruction->kind)
        {
        case BEGIN:
            add_begin_tag (output, indent, get_name (instruction),
                           instruction->u.begin.id);
            add_nl (output);
            indent += 4;
            break;
	    
        case END:
            indent -= 4;
            add_end_tag (output, indent, get_name (instruction));
            add_nl (output);
            break;
	    
        case VALUE:
            add_begin_tag (output, indent, get_name (instruction), -1);

	    if (stype_is_integer (instruction->type))
            {
                add_integer (output, instruction->u.integer.value);
	    }
	    else if (stype_is_pointer (instruction->type))
	    {
                add_integer (output, instruction->u.pointer.target_id);
	    }
	    else if (stype_is_string (instruction->type))
	    {
                add_string (output, instruction->u.string.value);
            }

            add_end_tag (output, 0, get_name (instruction));

	    add_nl (output);
            break;
        }
    }
    
#if 0
    /* FIXME - not10: bz2 compressing the output is probably
     * interesting at some point. For now just make sure
     * it works without actually using it.
     */
    bz2_compress (output->str, output->len,
                  &compressed, &compressed_size);
    
    g_free (compressed);
#endif
    
    retval = g_file_set_contents (filename, output->str, output->len, err);
    
    g_string_free (output, TRUE);
    
    return retval;
}


void
sfile_input_free (SFileInput *file)
{
    free_instructions (file->instructions, file->n_instructions);
    
    g_hash_table_destroy (file->instructions_by_location);
    
    g_free (file);
}

void
sfile_output_free (SFileOutput *sfile)
{
    Instruction *instructions;
    int n_instructions;
    
    n_instructions = sfile->instructions->len;
    instructions = (Instruction *)g_array_free (sfile->instructions, FALSE);
    
    free_instructions (instructions, n_instructions);
    
    g_hash_table_destroy (sfile->objects);
    g_free (sfile);
}