gistfile1.sql

CREATE FUNCTION apply_hunks(content text[], page_id int,
    min_revision int, max_revision int, reverse boolean DEFAULT FALSE)
    RETURNS text[] as $$
declare
    hunk record;
    revision int := null;
    offset int := 0;
    start int;
    length int;
    content_line text;
    hunk_line text;
    hunk_content_line text;
    marker char(1);
    applied_hunk text[];
    content_length int;
begin
    FOR hunk in SELECT * 
        FROM page_diff_hunk AS hunk
        WHERE hunk.page_id = page_id
        AND hunk.revision >= min_revision
        AND hunk.revision < max_revision
        ORDER BY hunk.revision DESC, hunk.start ASC
    LOOP
        IF revision != hunk.revision THEN
            revision := hunk.revision;
            -- reset offset
            offset := 0;
        END IF;
        start := hunk.start + "offset";
        content_line := content[start];
        FOREACH hunk_line IN ARRAY string_to_array(hunk.content, E'\n') LOOP
            marker = left(hunk_line, 1);
            hunk_content_line = substr(hunk_line, 2);
            IF (marker = ' ') or (marker = '+' and not reverse) or (marker = '-' and reverse) THEN
                applied_hunk := array_append(applied_hunk, hunk_content_line);
            END IF;
        END LOOP;
        -- replace content array
        content_length := array_length(content, 1);
        content := content[1:hunk.start] + applied_hunk + 
            content[start:content_length];
    END LOOP;
    RETURN content;
end;
$$ language plpgsql
STABLE STRICT;

CREATE FUNCTION apply_hunks_cursor(content text[], hunks refcursor,
    reverse boolean DEFAULT FALSE) returns text[] AS $$
declare
    hunk record;
    revision int := null;
    offset int := 0;
    start int;
    length int;
    content_line text;
    hunk_line text;
    hunk_content_line text;
    marker char(1);
    applied_hunk text[];
    content_length int;
begin
    FOR hunk IN hunks LOOP
        IF revision != hunk.revision THEN
            revision := hunk.revision;
            -- reset offset
            offset := 0;
        END IF;
        start := hunk.start + "offset";
        content_line := content[start];
        FOREACH hunk_line IN ARRAY string_to_array(hunk.content, E'\n') LOOP
            marker = left(hunk_line, 1);
            hunk_content_line = substr(hunk_line, 2);
            IF (marker = ' ') or (marker = '+' and not reverse) or (marker = '-' and reverse) THEN
                applied_hunk := array_append(applied_hunk, hunk_content_line);
            END IF;
        END LOOP;
        -- replace content array
        content_length := array_length(content, 1);
        content := content[1:hunk.start] + applied_hunk + 
            content[start:content_length];
    END LOOP;
    RETURN content;
end;
$$ language plpgsql
STABLE STRICT;